CHAPTER XIV.[1] ASSOCIATION.

After discrimination, association! Already in the last chapter I have had to invoke, in order to explain the improvement of certain discriminations by practice, the 'association' of the objects to be distinguished, with other more widely differing ones. It is obvious that the advance of our knowledge must consist of both operations; for objects at first appearing as wholes are analyzed into parts, and objects appearing separately are brought together and appear as new compound wholes to the mind. Analysis and synthesis are thus the incessantly alternating mental activities, a stroke of the one preparing the way for a stroke of the other, much as, in walking, a man's two legs are alternately brought into use, both being indispensable for any orderly advance.

The manner in which trains of imagery and consideration follow each other through our thinking, the restless flight of one idea before the next, the transitions our minds make between things wide as the poles asunder, transitions which at first sight startle us by their abruptness, but which, when scrutinized closely, often reveal intermediating links of perfect naturalness and propriety -- all this magical, imponderable streaming has from time immemorial excited the admiration of all whose attention happened to be caught by its omnipresent mystery. And it has furthermore challenged the race of philosophers to banish something of the mystery by formulating the process in simpler terms. The problem which the philosophers have set themselves is that of ascertaining principles of connection between the thoughts which thus appear to sprout one out of the other, whereby their peculiar succession or coexistence may be explained.

But immediately an ambiguity arises: which sort of connection is meant? connection thought-of, or connection between thoughts? These are two entirely different things, and only in the case of one of them is there any hope of finding 'principles.' The jungle of connections thought of can never be formulated simply. Every conceivable connection may be thought of -- of coexistence, succession, resemblance, contrast, contradiction, cause and effect, means and end, genus and species, part and whole, substance and property, early and late, large and small, landlord and tenant, master and servant, -- Heaven knows what, for the list is literally inexhaustible. The only simplification which could possibly be aimed at would be the reduction of the relations to a smaller number of types, like those which such authors as Kant and Renouvier call the 'categories' of the understanding.[2] According as we followed one category or another we should sweep, with our thought, through the world in this way or in that. And all the categories would be logical, would be relations of reason. They would fuse the items into a continuum. Were this the sort of connection sought between one moment of our thinking and another, our chapter might end here. For the only summary description of these infinite possibilities of transition, is that they are all acts of reason, and that the mind proceeds from one object to another by some rational path of connection. The trueness of this formula is only equalled by its sterility, for psychological purposes. Practically it amounts to simply referring the inquirer to the relations between facts or things, and to telling him that his thinking follows them.

But as a matter of fact, his thinking only sometimes follows them, and these so-called 'transitions of reason' are far from being all alike reasonable. If pure thought runs all our trains, why should she run some so fast and some so slow, some through dull flats and some through gorgeous scenery, some to mountain-heights and jewelled mines, others through dismal swamps and darkness? -- and run some off the track altogether, and into the wilderness of lunacy? Why do we spend years straining after a certain scientific or practical problem, but all in vain -- thought refusing to evoke the solution we desire? And why, some day, walking in the street with our attention miles away from that quest, does the answer saunter into our minds as carelessly as if it had never been called for -- suggested, possibly, by the flowers on the bonnet of the lady in front of us, or possibly by nothing that we can discover? If reason can give us relief then, why did she not do so earlier?

The truth must be admitted that thought works under conditions imposed ab extra. The great law of habit itself -- that twenty experiences make us recall a thing better than one, that long indulgence in error makes right thinking almost impossible -- seems to have no essential foundation in reason. The business of thought is with truth -- the number of experiences ought to have nothing to do with her hold of it; and she ought by right to be able to hug it all the closer, after years wasted out of its presence. The contrary arrangements seem quite fantastic and arbitrary, but nevertheless are part of the very bone and marrow of our minds. Reason is only one out of a thousand possibilities in the thinking of each of us. Who can count all the silly fancies, the grotesque suppositions, the utterly irrelevant reflections he makes in the course of a day? Who can swear that his prejudices and irrational beliefs constitute a less bulky part of his mental furniture than his clarified opinions? It is true that a presiding arbiter seems to sit aloft in the mind, and emphasize the better suggestions into permanence, while it ends by droopping out and leaving unrecorded the confusion. But this is all the difference. The mode of genesis of the worthy and the worthless seems the same. The laws of our actual thinking, of the cogitatum, must account alike for the bad and the good materials on which the arbiter has to decide, for wisdom and for folly. The laws of the arbiter, of the cogitandum, of what we ought to think, are to the former as the laws of ethics are to those of history. Who but an hegelian historian ever pretended that reason in action was per se a sufficient explanation of the political changes in Europe?

There are, then, mechanical conditions on which thought depends, and which, to say the least, determine the order in which is presented the content or material for her comparisons, selections, and decisions. It is a suggestive fact that Locke, and many more recent Continental psychologists, have found themselves obliged to invoke a mechanical process to account for the aberrations of thought, the obstructive preprocessions, the frustrations of reason. This they found in the law of habit, or what we now call Association by Contiguity. But it never occurred to these writers that a process which could go the length of actually producing some ideas and sequences in the mind might safely be trusted to produce others too; and that those habitual associations which further thought may also come from the same mechanical source as those which hinder it. Hartley accordingly suggested habit as a sufficient explanation of all connections of our thoughts, and in so doing planted himself squarely upon the properly psychological aspect of the problem of connection, and sought to treat both rational and irrational connections from a single point of view. The problem which he essayed, however lamely, to answer, was that of the connection between our psychic states considered purely as such, regardless of the objective connections of which they might take cognizance. How does a man come, after thinking of A, to think of B the next moment? or how does he come to think A and B always together? These were the phenomena which Hartley undertook to explain by cerebral physiology. I believe that he was, in many essential respects, on the right track, and I propose simply to revise his conclusions by the aid of distinctions which he did not make.

But the whole historic doctrine of psychological association is tainted with one huge error -- that of the construction of our thoughts out of the compounding of themselves together of immutable and incessantly recurring 'simple ideas.' It is the cohesion of these which the 'principles of association' are considered to account for. In Chapters VI and IX we saw abundant reasons for treating the doctrine of simple ideas or psychic atoms as mythological; and, in all that follows, our problem will be to keep whatever truths the associationist doctrine has caught sight of without weighing it down with the untenable incumbrance that the association is between 'ideas.'

Association, so far as the word stands for an effect, is between THINGS THOUGHT OF -- it is THINGS, not ideas, which are associated in the mind. We ought to talk of the association of objects, not of the association of ideas. And so far as association stands for a cause, it is between processes in the brain -- it is these which, by being associated in certain ways, determine what successive objects shall be thought. Let us proceed towards our final generalization by surveying first a few familiar facts.

The laws of motor habit in the lower centres of the nervous system are disputed by no one. A series of movements repeated in a certain order tend to unroll themselves with peculiar ease in that order for ever afterward. Number one awakens number two, and that awakens number three, and so on, till the last is produced. A habit of this kind once become inveterate may go on automatically. And so it is with the objects with which our thinking is concerned. With some persons each note of a melody, heard but once, will accurately revive in its proper sequence. Small boys at school learn the inflections of many a Greek noun, adjective, or verb, from the reiterated recitations of the upper classes falling on their ear as they sit at their desks. All this happens with no voluntary effort on their part and with no thought of the spelling of the words. The doggerel rhymes which children use in their games, such as the formula

"Ana mana mona mike Barcelona bona strike,"

used for 'counting out,' form another familiar example of things heard in sequence cohering in the same order in the memory.

In touch we have a smaller number of instances, though probably every one who bathes himself in a certain fixed manner is familiar with the fact that each part of his body over which the water is squeezed from the sponge awakens a premonitory tingling consciousness in that portion of skin which is habitually the next to be deluged. Tastes and smells form no very habitual series in our experience. But even if they did, it is doubtful whether habit would fix the order of their reproduction quite so well as it does that of other sensations. In vision, however, we have a sense in which the order of reproduced things is very nearly as much influenced by habit as is the order of remembered sounds. Rooms, landscapes, buildings, pictures, or persons with whose look we are very familiar, surge up before the mind's eye with all the details of their appearance complete, so soon as we think of any one of their component parts. Some persons, in reciting printed matter by heart, will seem to see each successive word, before they utter it, appear in its order on an imaginary page. A certain chess-player, one of those heroes who train themselves to play several games at once blindfold, is reported to say that in bed at night after a match the games are played all over again before his mental eye, each board being pictured as passing in turn through each of its successive stages. In this case, of course, the intense previous voluntary strain of the power of visual representation is what facilitated the fixed order of revival.

Association occurs as amply between impressions of different senses as between homogeneous sensations. Seen things and heard things cohere with each other, and with odors and tastes, in representation, in the same order in which they cohered as impressions of the outer world. Feelings of contact reproduce similarly the sights, sounds, and tastes with which experience has associated them. In fact, the 'objects' of our perception, as trees, men, houses, microscopes, of which the real world seems composed, are nothing but clusters of qualities which through simultaneous stimulation have so coalesced that the moment one is excited actually it serves as a sign or cue for the idea of the others to arise. Let a person enter his room in the dark and grope among the objects there. The touch of the matches will instantaneously recall their appearance. If his hand comes in contact with an orange on the table, the golden yellow of the fruit, its savor and perfume will forthwith shoot through his mind. In passing the hand over the sideboard or in jogging the coal-scuttle with the foot, the large glossy dark shape of the one and the irregular blackness of the other awaken like a flash and constitute what we call the recognition of the objects. The voice of the violin faintly echoes through the mind as the hand is laid upon it in the dark, and the feeling of the garments or draperies which may hang about the room is not understood till the look correlative to the feeling has in each case been resuscitated. Smells notoriously have the power of recalling the other experiences in whose company they were wont to be felt, perhaps long years ago; and the voluminous emotional character assumed by the images which suddenly pour into the mind at such a time forms one of the staple topics of popular psychologic wonder --

"Lost and gone and lost and gone! A breath, a whisper -- some divine farewell -- Desolate sweetness -- far and far away."

We cannot hear the din of a railroad train or the yell of its whistle, without thinking of its long, jointed appearance and its headlong speed, nor catch a familiar voice in a crowd without recalling, with the name of the speaker, also his face. But the most notorious and important case of the mental combination of auditory with optical impressions originally experienced together is furnished by language. The child is offered a new and delicious fruit and is at the same time told that it is called a 'fig.' Or looking out of the window he exclaims, "What a funny horse!" and is told that it is a 'piebald' horse. When learning his letters, the sound of each is repeated to him whilst its shape is before his eye. Thenceforward, long as he may live, he will never see a fig, a piebald horse, or a letter of the alphabet without the name which he first heard in conjunction with each clinging to it in his mind; and inversely he will never hear the name without the faint arousal of the image of the object.[3]

THE RAPIDITY OF ASSOCIATION.

Reading exemplifies this kind of cohesion even more beautifully. It is an uninterrupted and protracted recall of sounds by sights which have always been coupled with them in the past. I find that I can name six hundred letters in two minutes on a printed page. Five distinct acts of association between sight and sound (not to speak of all the other processes concerned) must then have occurred in each second in my mind. In reading entire words the speed is much more rapid. Valentin relates in his Physiology that the reading of a single page of the proof, containing 2629 letters, took him 1 minute and 32 seconds. In this experiment each letter was understood in 1/28 of a second, but owing to the integration of letters into entire words, forming each a single aggregate impression directly associated with a single acoustic image, we need not suppose as many as 28 separate associations in a sound. The figures, however, suffice to show with what extreme rapidity an actual sensation recalls its customary associates. Both in fact seem to our ordinary attention to come into the mind at once.

The time-measuring psychologists of recent days have tried their hand at this problem by more elaborate methods. Galton, using a very simple apparatus, found that the sight of an unforeseen word would awaken an associated 'idea' in about 5/6 of a second.[4] Wundt next made determinations in which the 'cue' was given by single-syllabled words called out by an assistant. The person experimented on had to press a key as soon as the sound of the word awakened an associated idea. Both word and reaction were chronographically registered, and the total time-interval between the two amounted, in four observers, to 1.009, 0.896, 1.037, and 1.154 seconds respectively. From this the simple physiological reaction-time and the time of merely identifying the word's sound (the 'apperception-time,' as Wundt calls it) must be subtracted, to get the exact time required for the associated idea to arise. These times were separately determined and subtracted. The difference, called by Wundt the association-time, amounted, in the same four persons, to 706, 723, 752, and 874 thousandths of a second respectively.[5] The length of the last figure is due to the fact that the person reacting (President G. S. Hall) was an American, whose associations with German words would naturally be slower than those of natives. The shortest association-time noted was when the word 'Sturm' suggested to Prof. Wundt the word 'Wind' in 0.341 second.[6] -- Finally, Mr. Cattell made some interesting observations upon the association-time between the look of letters and their names. "I pasted letters," he says, "on a revolving drum, and determined at what rate they could be read aloud as they passed by a slit in a screen." He found it to vary according as one, or more than one letter, was visible at a time through the slit, and gives half a second as about the time which it takes to see and name a single letter seen alone.

"When two or more letters are always in view, not only do the processes of seeing and naming overlap, but while the subject is seeing one letter he begins to see the ones next following, and so can read them more quickly. Of the nine persons experimented on, four could read the letters faster when five were in view at once, but were not helped by a sixth letter; three were not helped by a fifth, and two not by a fourth letter. This shows that while one idea is in the centre, two, three, or four additional ideas may be in the background of consciousness. The second letter in view shortens the time about 1/40, the third 1/60, the fourth 1/100, the fifth 1/200 sec.

"I find it takes about twice as long to read (aloud, as fast as possible) words which have no connection as words which make sentences, and letters which have no connection as letters which make words. When the words make sentences and the letters words, not only do the processes of seeing and naming overlap, but by one mental effort the subject can recognize a whole group of words or letters, and by one will-act choose the motions to be made in naming, so that the rate at which the words and letters are read is really only limited by the maximum rapidity at which the speech-organs can be moved. As the result of a large number of experiments, the writer found that he had read words not making sentences at the rate of 1/4 sec., words making sentences (a passage from Swift) at the rate of 1/8 sec., per word.... The rate at which a person reads a foreign language is proportional to his familiarity with the language. For example, when reading as fast as possible the writer's rate was, English 138, French 167, German 250, Italian 327, Latin 434, and Greek 484; the figures giving the thousandths of a second taken to read each word. Experiments made on others strikingly confirm these results. The subject does not know that he is reading the foreign language more slowly than his own; this explains why foreigners seem to talk so fast. This simple method of determining a person's familiarity with a language might be used in school examinations.

"The time required to see and name colors and pictures of objects was determined in the same way. The time was found to be about the same (over 1/2 sec.) for colors as for pictures, and about twice as long as for words and letters. Other experiments I have made show that we can recognize a single color or picture in a slightly shorter time than a word or letter, but take longer to name it. This is because, in the case or words and letters, the association between the idea and name has taken place so often that the process has become automatic, whereas in the case of colors and pictures we must by a voluntary effort choose the name.[7]

In later experiments Mr. Cattell studied the time for various associations to be performed, the termini (i.e., cue and answer) being words. A word in one language was to call up its equivalent in another, the name of an author the tongue in which he wrote, that of a city the country in which it lay, that of a writer one of his works, etc. The mean variation from the average is very great in all these experiments; and the interesting feature which they show is the existence of certain constant differences between associations of different sorts. Thus:

From country to city, Mr. C.'s time was 0.340 sec. " season " month " " " 0.399 " language " author, " " " 0.523 " author " work, " " " 0.596 The average time of two observers, experimenting on eight different types of association, was 0.420 and 0.436 sec. respectively.[8] The very wide range of variation is undoubtedly a consequence of the fact that the words used as cues, and the different types of association studied, differ much in their degree of familiarity.

"For example, B is a teacher of mathematics; C has busied himself more with literature. C knows quite as well as B that 7 + 5 = 12, yet he needs 1/10 of a second longer to call it to mind; B knows quite as well as C that Dante was a poet, but needs 1/20 of a second longer to think of it. Such experiments lay bare the mental life in a way that is startling and not always gratifying."[9]

THE LAW OF CONTIGUITY.

Time-determinations apart, the facts we have run over can all be summed up in the simple statement that objects once experienced together tend to become associated in the imagination, so that when any one of them is thought of, the others are likely to be thought of also, in the same order of sequence or coexistence as before. This statement we may name the law of mental association by contiguity.[10]

I preserve this name in order to depart as little as possible from tradition, although Mr. Ward's designation of the process as that of association by continuity[11] or Wundt's as that of external association (to distinguish it from the internal association which we shall presently learn to know under the name of association by similarity)[12] are perhaps better terms. Whatever we name the law, since it expresses merely a phenomenon of mental habit, the most natural way of accounting for it is to conceive it as a result of the laws of habit in the nervous system; in other words, it is to ascribe it to a physiological cause. If it be truly a law of those nerve-centres which co-ordinate sensory and motor processes together that paths once used for coupling any pair of them are thereby made more permeable, there appears no reason why the same law should not hold good of ideational centres and their coupling-paths as well.[13] Parts of these centres which have once been in action together will thus grow so linked that excitement at one point will irradiate through the system. The chances of complete irradiation will be strong in proportion as the previous excitements have been frequent, and as the present points excited afresh are numerous. If all points were originally excited together, the irradiation may be sensibly simultaneous throughout the system, when any single point or group of points is touched off. But where the original impressions were successive -- the conjugation of a Greek verb, for example -- awakening nerve-tracts in a definite order, they will now, when one of them awakens, discharge into each other in that definite order and in no other way.

The reader will recollect all that has been said of increased tension in nerve-tracts and of the summation of stimuli (p. 82 ff.). We must therefore suppose that in these ideational tracts as well as elsewhere, activity may be awakened, in any particular locality, by the summation therein of a number of tensions, each incapable alone of provoking an actual discharge. Suppose for example the locality M to be in functional continuity with four other localities, K, L, N, and O. Suppose moreover that on four previous occasions it has been separately combined with each of these localities in a common activity. M may then be indirectly awakened by any cause which tends to awaken either K, L, N, or O. But if the cause which awakens K, for instance, be so slight as only to increase its tension without arousing it to full discharge, K will only succeed in slightly increasing the tension of M. But if at the same time the tensions of L, N, and O are similarly increased, the combined effects of all four upon M may be so great as to awaken an actual discharge in this latter locality. In like manner if the paths between M and the four other localities have been so slightly excavated by previous experience as to require a very intense excitement in either of the localities before M can be awakened, a less strong excitement than this in any one will fail to reach M. But if all four at once are mildly excited, their compound effect on M may be adequate to its full arousal.

The psychological law of association of objects thought of through their previous contiguity in thought or experience would thus be an effect, within the mind, of the physical fact that nerve-currents propagate themselves easiest through those tracts of conduction which have been already most in use. Descartes and Locke hit upon this explanation, which modern science has not yet succeeded in improving.

"Custom," says Locke, "settles habits of thinking in the understanding, as well as of determining in the will, and of motions in the body; all which seem to be but trains of motion in the animal spirits [by this Locke meant identically what we understand by neural processes] which, once set agoing, continue in the same steps they have been used to, which by often treading are worn into a smooth path, and the motion in it becomes easy and, as it were, natural."[14]

Hartley was more thorough in his grasp of the principle. The sensorial nerve-currents, produced when objects are fully present, were for him 'vibrations,' and those which produce ideas of objects in their absence were 'miniature vibrations.' And he sums up the cause of mental association in a single formula by saying:

"Any vibrations, A, B, C, etc., by being associated together a sufficient Number of Times, get such a Power over a, b, c, etc., the corresponding Miniature Vibrations, that any of the Vibrations A, when impressed alone, shall be able to excite b, c, etc., the Miniatures of the rest."[15]

It is evident that if there be any law of neural habit similar to this, the contiguities, coexistences, and successions, met with in outer experience, must inevitably be copied more or less perfectly in our thought. If A B C D E be a sequence of outer impressions (they may be events or they may be successively experienced properties of an object) which once gave rise to the successive 'ideas,' a b c d e, then no sooner will A impress us again and awaken the a, than b c d e will arise as ideas even before B C D E have come in as impressions. In other words, the order of impressions will the next time be anticipated; and the mental order will so far forth copy the order of the outer world. Any object when met again will make us expect its former concomitants, through the overflowing of its brain-tract into the paths which lead to theirs. And all these suggestions will be effects of a material law.

Where the associations are, as here, of successively appearing things, the distinction I made at the outset of the chapter, between a connection thought of and a connection of thoughts, is unimportant. For the connection thought of is concomitance or succession; and the connection between the thoughts is just the same. The 'objects' and the 'ideas' fit into parallel schemes, and may be described in identical language, as contiguous things tending to be thought again together, or contiguous ideas tending to recur together.

Now were these cases fair samples of all association, the distinction I drew might well be termed a Spitzfindigkeit or piece of pedantic hair-splitting, and be dropped. But as a matter of fact we cannot treat the subject so simply. The same outer object may suggest either of many realities formerly associated with it -- for in the vicissitudes of our outer experience we are constantly liable to meet the same thing in the midst of differing companions -- and a philosophy of association that should merely say that it will suggest one of these, or even of that one of them which it has oftenest accompanied, would go but a very short way into the rationale of the subject. This, however, is about as far as most associationists have gone with their 'principle of contiguity.' Granted an object, A, they never tell us beforehand which of its associates it will suggest; their wisdom is limited to showing, after it has suggested a second object, that that object was once an associate. They have had to supplement their principle of Contiguity by other princi- ples, such as those of Similarity and Contrast, before they could begin to do justice to the richness of the facts.

THE ELEMENTARY LAW OF ASSOCIATION.

I shall try to show, in the pages which immediately follow, that there is no other elementary causal law of association than the law of neural habit. All the materials of our thought are due to the way in which one elementary process of the cerebral hemispheres tends to excite whatever other elementary process it may have excited at some former time. The number of elementary processes at work, however, and the nature of those which at any time are fully effective in rousing the others, determine the character of the total brain-action, and, as a consequence of this, they determine the object thought of at the time. According as this resultant object is one thing or another, we call it a product of association by contiguity or of association by similarity, or contrast, or whatever other sorts we may have recognized as ultimate. Its production, however, is, in each one of these cases, to be explained by a merely quantitative variation in the elementary brain-processes momentarily at work under the law of habit, so that psychic contiguity, similarity, etc., are derivatives of a single profounder kind of fact.

My thesis, stated thus briefly, will soon become more clear; and at the same time certain disturbing factors, which co-operate with the law of neural habit, will come to view.

Let us then assume as the basis of all our subsequent reasoning this law: When two elementary brain-processes have been active together or in immediate succession, one of them, on reoccurring, tends to propagate its excitement into the other.

But, as a matter of fact, every elementary process has found itself at different times excited in conjunction with many other processes, and this by unavoidable outward causes. Which of these others it shall awaken now becomes a problem. Shall b or c be aroused next by the present a? We must make a further postulate, based, however, on the fact of tension in nerve-tissue, and on the fact of summation of excitements, each incomplete or latent in itself, into an open resultant.[16] The process b, rather than c, will awake, if in addition to the vibrating tract a some other tract d is in a state of sub-excitement, and formerly was excited with b alone and not with a. In short, we may say:

The amount of activity at any given point in the brain-cortex is the sum of the tendencies of all other points to discharge into it, such tendencies being proportionate (1) to the number of times the excitement of each other point may have accompanied that of the point in question; (2) to the intensity of such excitements; and (3) to the absence of any rival point functionally disconnected with the first point, into which the discharges might be diverted.

Expressing the fundamental law in this most complicated way leads to the greatest ultimate simplification. Let us, for the present, only treat of spontaneous trains of thought and ideation, such as occur in revery or musing. The case of voluntary thinking toward a certain end shall come up later.

Take, to fix our ideas, the two verses from 'Locksley Hall':

"I, the heir of all the ages in the foremost files of time,"

and --

"For I doubt not through the ages one increasing purpose runs."

Why is it that when we recite from memory one of these lines, and get as far as the ages, that portion of the other lines which follows, and, so to speak, sprouts out of the ages, does not also sprout out of our memory, and confuse the sense of our words? Simply because the word that follows the ages has its brain-process awakened not simply by the brain-process of the ages alone, but by it plus the brain-processes of all the words preceding the ages. The word ages at its moment of strongest activity would, per se, indifferently discharge into either 'in' or 'one.' So would the previous words (whose tension is momentarily much less stronger than that of ages) each of them indifferently dis- charge into either of a large number of other words with which they have been at different times combined. But when the processes of 'I, the heir of all the ages,' simultaneously vibrate in the brain, the last one of them in a maximal, the others in a fading phase of excitement; then the strongest line of discharge will be that which they all alike tend to take. 'In' and not 'one' or any other word will be the next to awaken, for its brain-process has previously vibrated in unison not only with that of ages, but with that of all those other words whose activity is dying away. It is a good case of the effectiveness over thought of what we called on p. 258 a 'fringe.'

But if some one of these preceding words -- 'heir,' for example -- had an intensely strong association with some brain-tracts entirely disjoined in experience from the poem of 'Locksley Hall' -- if the reciter, for instance, were tremulously awaiting the opening of a will which might make him a millionaire -- it is probable that the path of discharge through the words of the poem would be suddenly interrupted at the word 'heir.' His emotional interest in that word would be such that its own special associations would prevail over the combined ones of the other words. He would, as we say, be abruptly reminded of his personal situation, and the poem would lapse altogether from his thoughts.

The writer of these pages has every year to learn the names of a large number of students who sit in alphabetical order in a lecture-room. He finally learns to call them by name, as they sit in their accustomed places. On meeting one in the street, however early in the year, the face hardly ever recalls the name, but it may recall the place of its owner in the lecture-room, his neighbors' faces, and consequently his general alphabetical position; and then, usually as the common associate of all these combined data, the student's name surges up in his mind.

A father wishes to show to some guests the progress of his rather dull child in Kindergarten instruction. Holding the knife upright on the table, he says, "What do you call that, my boy?" "I calls it a knife, I does," is the sturdy reply, from which the child cannot be induced to swerve by any alteration in the form of question, until the father recollecting that in the Kindergarten a pencil was used, and not a knife, draws a long one from his pocket, holds it in the same way, and then gets the wished-for answer, "I calls it vertical." All the concomitants of the Kindergarten experience had to recombine their effect before the word 'vertical' could be reawakened.

Professor Bain, in his chapters on 'Compound Association,' has treated in a minute and exhaustive way of this type of mental sequence, and what he has done so well need not be here repeated.[17]

Impartial Redintegration.

The ideal working of the law of compound association, were it unmodified by any extraneous influence, would be such as to keep the mind in a perpetual treadmill of concrete reminiscences from which no detail could be omitted. Suppose, for example, we begin by thinking of a certain dinner-party. The only thing which all the components of the dinner-party could combine to recall would be the first concrete occurrence which ensued upon it. All the details of this occurrence could in turn only combine to awaken the next following occurrence, and so on. If a, b, c, d, e, for instance, be the elementary nerve-tracts excited by the last act of the dinner-party, call this act A, and l, m, n, o, p be those of walking home through the frosty night, which we may call B, then the thought of A must awaken that of B, because a, b, c, d, e, will each and all discharge into l through the paths by which their original discharge took place. Similarly they will discharge into m, n, o, and p; and these latter tracts will also each reinforce the other's action because, in the experience B, they have already vibrated in unison. The lines in Fig. 40, p. 570, symbolize the summation of discharges into each of the components of B, and the consequent strength of the combination of influences by which B in its totality is awakened.

Hamilton first used the word 'redintegration' to designate all association. Such processes as we have just de- scribed might in an emphatic sense be termed redintegrations, for they would necessarily lead, if unobstructed, to the reinstatement in thought of the entire content of large trains of past experience. From this complete redintegration there could be no escape save through the irruption of some new and strong present impression of the senses, or through the excessive tendency of some one of the elementary brain-tracts to discharge independently into an aberrant quarter of the brain. Such was the tendency of the word 'heir' in the verse from 'Locksley Hall,' which was our first example.

How such tendencies are constituted we shall have soon to inquire with some care. Unless they are present, the panorama of the past, once opened, must unroll itself with fatal literality to the end, unless some outward sound, sight, or touch divert the current of thought.

Let us call this process impartial redintegration. Whether it ever occurs in an absolutely complete form is doubtful. We all immediately recognize, however, that in some minds there is a much greater tendency than in others for the flow of thought to take this form. Those insufferably garrulous old women, those dry and fanciless beings who spare you no detail, however petty, of the facts they are recounting, and upon the thread of whose narrative all the irrelevant items cluster as pertinaciously as the essential ones, the slaves of literal fact, the stumblers over the smallest abrupt step in thought, are figures known to all of us. Comic literature has made her profit out of them. Juliet's nurse is a classical example. George Eliot's village characters and some of Dicken's minor personages supply excellent instances.

Perhaps as successful a rendering as any of this mental type is the character of Miss Bates in Miss Austen's 'Emma.' Hear how she redintegrates:

"'But where could you hear it?' cried Miss Bates. 'Where could you possibly hear it, Mr. Knightley? For it is not five minutes since I received Mrs. Cole's note -- no, it cannot be more than five -- or at least ten -- for I had got my bonnet and spencer on, just ready to come out -- I was only gone down to speak to Patty agian about the pork -- Jane was standing in the passage -- were not you, Jane? -- for my mother was so afraid that we had not any salting-pan large enough. So I said I would go down and see, and Jane said: "Shall I go down instead? for I think you have a little cold, and Patty has been washing the kitchen." "Oh, my dear," said I -- well, and just then came the note. A Miss Hawkins -- that's all I know -- a Miss Hawkins, of Bath. But, Mr. Knightley, how could you possibly have heard it? for the very moment Mr. Cole told Mrs. Cole of it, she sat down and wrote to me. A Miss Hawkins --'"

But in every one of us there are moments when this complete reproduction of all the items of a past experience occurs. What are those moments? They are moments of emotional recall of the past as something which once was, but is gone for ever -- moments, the interest of which consists in the feeling that our self was once other than it now is. When this is the case, any detail, however minute, which will make the past picture more complete, will also have its effect in swelling that total contrast between now and then which forms the central interest of our contemplation.

ORDINARY OR MIXED ASSOCIATION.

This case helps us to understand why it is that the ordinary spontaneous flow of our ideas does not follow the law of impartial redintegration. In no revival of a past experience are all the items of our thought equally operative in determining what the next thought shall be. Always some ingredient is prepotent over the rest. Its special suggestions or associations in this case will often be different from those which it has in common with the whole group of items; and its tendency to awaken these outlying associates will deflect the path of our revery. Just as in the original sensible experience our attention focalized itself upon a few of the impressions of the scene before us, so here in the reproduction of those impressions an equal partiality is shown, and some items are emphasized above the rest. What these items shall be is, in most cases of spontaneous revery, hard to determine beforehand. In subjective terms we say that the prepotent items are those which appeal most to our INTEREST.

Expressed in brain-terms, the law of interest will be: some one brain-process is always prepotent above its concomitants in arousing action elsewhere.

"Two processes," says Mr. Hodgson,[18] "are constantly going on in redintegration. The one a process of corrosion, melting, decay; the other a process of renewing, arising, becoming.... No object of representation remains long before consciousness in the same state, but fades, decays, and becomes indistinct. Those parts of the object, however, which possess an interest resist this tendency to gradual decay of the whole object.... This inequality in the object -- some parts, the uninteresting, submitting to decay; others, the interesting parts, resisting it -- when it has continued for a certain time, ends in becoming a new object."

Only where the interest is diffused equally over all the parts (as in the emotional memory just referred to, where, as all past, they all interest us alike) is this law departed from. It will be least obeyed by those minds which have the smallest variety and intensity of interests -- those who, by the general flatness and poverty of their æsthetic nature, are kept for ever rotating among the literal sequences of their local an personal history.

Most of us, however, are better organized than this, and our musings pursue and erratic course, swerving continually into some new direction traced by the shifting play of interest as it ever falls on some partial item in each complex representation that is evoked. Thus it so often comes about that we find ourselves thinking at two nearly adjacent moments of things separated by the whole diameter of space and time. Not till we carefully recall each step of our cogitation do we see how naturally we came by Hodgson's law to pass from one to the other. Thus, for instance, after looking at my clock just now (1879), I found myself thinking of a recent resolution in the Senate about our legal-tender notes. The clock called up the image of the man who had repaired its gong. He suggested the jeweller's shop where I had last seen him; that shop, some shirt-studs which I had bought there; they, the value of gold and its recent decline; the latter, the equal value of greenbacks, and this, naturally, the question of how long they were to last, and of the Bayard proposition. Each of these images offered various points of interest. Those which formed the turning-points of my thought are easily assigned. The gong was momentarily the most interesting part of the clock, because, from having begun with a beautiful tone, it had become discordant and aroused disappointment. But for this the clock might have suggested the friend who gave it to me, or any one of a thousand circumstances connected with clocks. The jeweller's shop suggested the studs, because they alone of all its contents were tinged with the egoistic interest of possession. This interest in the studs, their value, made me single out the material as its chief source, etc., to the end. Every reader who will arrest himself at any moment and say, "How came I to be thinking of just this?" will be sure to trace a train of representations linked together by lines of contiguity and points of interest inextricably combined. This is the ordinary process of the association of ideas as it spontaneously goes on in average minds. We may call it ORDINARY, or MIXED, ASSOCIATION.

Another example of it is given by Hobbes in a passage which has been quoted so often as to be classical:

"In a discourse of our present civil war, what could seem more impertinent than to ask (as one did) what was the value of a Roman penny? Yet the coherence to me was manifest enough. For the thought of the war introduced the thought of the delivering up the King to his enemies; the thought of that brought in the thought of the delivering up of Christ; and that again the thought of the thirty pence, which was the price of that treason: and thence easily followed that malicious question; and all this in a moment of time; for thought is quick."[19]

Can we determine, now, when a certain portion of the going thought has, by dint of its interest, become so prepotent as to make its own exclusive associates the dominant features of the coming thought -- can we, I say, determine which of its own associates shall be evoked? For they are many. As Hodgson says:

"The interesting parts of the decaying object are free to combine again with any objects or parts of objects with which at any time they have been combined before. All the former combinations of these parts may come back into consciousness; one must; but which will?"

Mr. Hodgson replies:

"There can be but one answer: that which has been most habitually combined with them before. This new object begins at once to form itself in consciousness, and to group its part round the part still remaining from the former object; part after part comes out and arranges itself in its old position; but scarcely has the process begun, when the original law of interest begins to operate on this new formation, seizes on the interesting parts and impresses them on the attention to the exclusion of the rest, and the whole process is repeated again with endless variety. I venture to propose this as a complete and true account of the whole process of redintegration."

In restricting the discharge from the interesting item into that channel which is simply most habitual in the sense of most frequent, Hodgson's account is assuredly imperfect. An image by no means always revives its most frequent associate, although frequency is certainly one of the most potent determinants of revival. If I abruptly utter the word swallow, the reader, if by habit an ornithologist, will think of a bird; if a physiologist or a medical specialist in throat diseases, he will think of deglutition. If I say date, he will, if a fruit-merchant or an Arabian traveller, think of the produce of the palm; if an habitual student of history, figures with A.D. or B.C. before them will rise in his mind. If I say bed, bath, morning, his own daily toilet will be invincibly suggested by the combined names of three of its habitual associates. But frequent lines of transition are often set at naught. The sight of C. Göring's 'System der kritischen Philosophie' has most frequently awakened in me thoughts of the opinions therein propounded. The idea of suicide has never been connected with the volumes. But a moment since, as my eye fell upon them, suicide was the thought that flashed into my mind. Why? Because but yesterday I received a letter from Leipzig informing me that this philosopher's recent death by drowning was an act of self-destruction. Thoughts tend, then, to awaken their most recent as well as their most habitual associates. This is a matter of notorious experience, too notorious, in fact, to need illustration. If we have seen our friend this morning, the mention of his name now recalls the circumstances of that interview, rather than any more remote details concerning him. If Shakespeare's plays are mentioned, and we were last night reading 'Richard II.,' vestiges of that play rather than of 'Hamlet' or 'Othello' float through our mind. Excitement of peculiar tracts, or peculiar modes of general excitement in the brain, leave a sort of tenderness or exalted sensibility behind them which takes days to die away. As long as it lasts, those tracts or those modes are liable to have their activities awakened by causes which at other times might leave them in repose. Hence, recency in experience is a prime factor in determining revival in thought.[20]

Vividness in an original experience may also have the same effect as habit or recency in bringing about likelihood of revival. If we have once witnessed an execution, any subsequent conversation or reading about capital punishment will almost certainly suggest images of that particular scene. Thus it is that events lived through only once, and in youth, may come in after-years, by reason of their exciting quality or emotional intensity, to serve as types or instances used by our mind to illustrate any and every occurring topic whose interest is most remotely pertinent to theirs. If a man in his boyhood once talked with Napoleon, any mention of great men or historical events, battles or thrones, or the whirligig of fortune, or islands in the ocean, will be apt to draw to his lips the incidents of that one memorable interview. If the word tooth now suddenly appears on the page before the reader's eye, there are fifty chances out of a hundred that, if he gives it time to awaken any image, it will be an image of some operation of dentistry in which he has been the sufferer. Daily he has touched his teeth and masticated with them; this very morning he brushed them, chewed his breakfast and picked them; but the rarer and remoter associations arise more promptly because they were so much more intense.[21]

A fourth factor in tracing the course of reproduction is congruity in emotional tone between the reproduced idea and our mood. The same objects do not recall the same associates when we are cheerful as when we are melancholy. Nothing, in fact, is more striking than our utter inability to keep up trains of joyous imagery when we are depressed in spirits. Storm, darkness, war, images of disease, poverty, and perishing afflict unremittingly the imaginations of melancholiacs. And those of sanguine temperament, when their spirits are high, find it impossible to give any permanence to evil forebodings or to gloomy thoughts. In an instant the train of association dances off to flowers and sunshine, and images of spring and hope. The records of Arctic or African travel perused in one mood awaken no thoughts but those of horror at the malignity of Nature; read at another time they suggest only enthusiastic reflections on the indomitable power and pluck of man. Few novels so overflow with joyous animal spirits as 'The Three Guardsmen' of Dumas. Yet it may awaken in the mind of a reader depressed with sea-sickness (as the writer can personally testify) a most dismal and woful consciousness of the cruelty and carnage of which heroes like Athos, Porthos, and Aramis make themselves guilty.

Habit, recency, vividness, and emotional congruity are, then, all reasons why one representation rather than another should be awakened by the interesting portion of a departing thought. We may say with truth that in the majority of cases the coming representation will have been either habitual, recent, or vivid, and will be congruous. If all these qualities unite in any one absent associate, we may predict almost infallibly that that associate of the going thought will form an important ingredient in the coming thought. In spite of the fact, however, that the succession of representations is thus redeemed from perfect indeterminism and limited to a few classes whose characteristic quality is fixed by the nature of our past experience, it must still be confessed that an immense number of terms in the linked chain of our representations fall outside of all assignable rule. To take the instance of the clock given on page 586. Why did the jeweller's shop suggest the shirt-studs rather than a chain which I had brought there more recently, which had cost more, and whose sentimental associations were much more interesting? Both chain and studs had excited brain-tracts simultaneously with the shop. The only reason why the nerve-stream from the shop-tract switched off into the stud-tract rather than into the chain-tract must be that the stud-tract happened at that moment to lie more open, either because of some accidental alteration in its nutrition or because the incipient sub-conscious tensions of the brain as a whole had so distributed their equilibrium that it was more unstable here than in the chain-tract. Any reader's introspection will easily furnish similar instances. It thus remains true that to a certain extent, even in those forms of ordinary mixed association which lie nearest to impartial redintegration, which associate of the interesting item shall emerge must be called largely a matter of accident -- accident, that is, for our intelligence. No doubt it is determined by cerebral causes, but they are too subtile and shifting for our analysis.

ASSOCIATION BY SIMILARITY.

In partial or mixed associations we have all along supposed the interesting portion of the disappearing thought to be of considerable extent, and to be sufficiently complex to constitute by itself a concrete object. Sir William Hamilton relates, for instance, that after thinking of Ben Lomond he found himself thinking of the Prussian system of education, and discovered that the links of association were a German gentleman whom he had met on Ben Lomond, Germany, etc. The interesting part of Ben Lomond, as he had experienced it, the part operative in determining the train of his ideas was the complex image of a particular man. But now let us suppose that that selective agency of interested attention, which may thus convert impartial redintegration into partial association -- let us suppose that it refines itself still further and accentuates a portion of the passing thought, so small as to be no longer the image of a concrete thing, but only of an abstract quality or property. Let us moreover suppose that the part thus accentuated persists in consciousness (or, in cerebral terms, has its brain-process continue) after the other portions of the thought have faded. This small surviving portion will then surround itself with its own associates after the fashion we have already seen, and the relation between the new thought's object and the object of the faded thought will be a relation of similarity. The pair of thoughts will form an instance of what is called 'Association by Similarity.'[22]

The similars which are here associated, or of which the first is followed by the second in the mind, are seen to be compounds. Experience proves that this is always the case. There is no tendency on the part of SIMPLE 'ideas,' attributes, or qualities to remind us of their like. The thought of one shade of blue does not remind us of that of another shade of blue, etc., unless indeed we have in mind some general purpose like naming the tint, when we should naturally think of other blues of the scale, through 'mixed association' of purpose, names, and tints, together. But there is no elementary tendency of pure qualities to awaken their similars in the mind.

We saw in the chapter on Discrimination that two compound things are similar when some one quality or group of qualities is shared alike by both, although as regards their other qualities they may have nothing in common. The moon is similar to a gas-jet, it is also similar to a football; but a gas-jet and a foot-ball are not similar to each other. When we affirm the similarity of two compound things, we should always say in what respect it obtains. Moon and gas-jet are similar in respect of luminosity, and nothing else; moon and foot-ball in respect of rotundity, and nothing else. Foot-ball and gas-jet are in no respect similar -- that is, they possess no common point, no identical attribute. Similarity, in compounds, is partial identity. When the same attribute appears in two phenomena, though it be their only common property, the two phenomena are similar is so far forth. To return now to our associated representations. If the thought of the moon is succeeded by the thought of a foot-ball, and that by the thought of one of Mr. X's railroads, it is because the attribute rotundity in the moon broke away from all the rest and surrounded itself with an entirely new set of companions -- elasticity, leathery integument, swift mobility in obedience to human caprice, etc.; and because the last-named attribute in the foot-ball in turn broke away from its companions, and, itself persisting, surrounded itself with such new attributes as make up the notions of a 'railroad king,' of a rising and falling stock-market, and the like.

The gradual passage from impartial redintegration to similar association through what we have called ordinary mixed association may be symbolized by diagrams. Fig. 41 is impartial redintegration, Fig. 42 is mixed, and Fig. 43 similar association. A in each is the passing, B the coming thought. In 'impartial,' all parts of A are equally operative in calling up B.

In 'mixed,' most parts of A are inert. The part M alone breaks out and awakens B.

In 'similar,' the focalized part M is much smaller than in the previous case, and after awakening its new set of associates, instead of fading out itself, it continues persistently active along with them, forming an identical part in the two ideas, and making these, pro tanto, resemble each other.

Why a single portion of the passing thought should break out from its concert with the rest and act, as we say, on its own hook, why the other parts should become inert, are mysteries which we can ascertain but not explain. Possibly a minuter insight into the laws of neural action will some day clear the matter up; possibly neural laws will not suffice, and we shall need to invoke a dynamic reaction of the form of consciousness upon its content. But into this we cannot enter now.

To sum up, then, we see that the difference between the three kinds of association reduces itself to a simple difference in the amount of that portion of the nerve-tract supporting the going thought which is operative in calling up the thought which comes. But the modus operandi of this active part is the same, be it large or be it small. The items constituting the coming object waken in every instance because their nerve-tracts once were excited continuously with those of the going object or its operative part. This ultimate physiological law of habit among the neural elements is what runs the train. The direction of its course and the form of its transitions, whether redintegrative, associative, or similar, are due to unknown regulative or determinative conditions which accomplish their effect by opening this switch and closing that, setting the engine sometimes at half-speed, and coupling or uncoupling cars.

This last figure of speech, into which I have glided unwittingly, affords itself an excellent instance of association by similarity. I was thinking of the deflections of the course of ideas. Now, from Hobbes's time downward, English writers have been fond of speaking of the train of our representations. This word happened to stand out in the midst of my complex thought with peculiarly sharp accentuation, and to surround itself with numerous details of railroad imagery. Only such details became clear, however, as had their nerve-tracts besieged by a double set of influences -- those from train on the one hand, and those from the movement of thought on the other. It may possibly be that the prepotency of the suggestions of the word train at this moment were due to the recent excitation of the railroad brain-tract by the instance chosen a few pages back of a railroad king playing foot-ball with the stock-market.

It is apparent from such an example how inextricably complex are all the contributory factors whose resultant is the line of our reverie. It would be folly in most cases to attempt to trace them out. From an instance like the above, where the pivot of the Similar Association was formed by a definite concrete word, train, to those where it is so subtile as utterly to elude our analysis, the passage is unbroken. We can form a series of examples. When Mr. Bagehot says that the mind of the savage, so far from being in a state of nature, is tattooed all over with monstrous superstitions, the case is very like the one we have just been considering. When Sir James Stephen compares our belief in the uniformity of nature, the congruity of the future with the past, to a man rowing one way and looking another, and steering his boat by keeping her stern in a line with an object behind him, the operative link becomes harder to dissect out. It is subtler still in Dr. Holmes's phrase, that stories in passing from mouth to mouth make a great deal of lee-way in proportion to their headway; or in Mr. Lowell's description of German sentences, that they have a way of yawing and going stern-foremost and not minding the helm for several minutes after it has been put down. And finally, it is a real puzzle when the color pale-blue is said to have feminine and blood-red masculine affinities. And if I hear a friend describe a certain family as having blotting-paper voices, the image, though immediately felt to be apposite, baffles the utmost powers of analysis. The higher poets all use abrupt epithets, which are alike intimate and remote, and, as Emerson says, sweetly torment us with invitations to their inaccessible homes.

In these latter instances we must suppose that there is an identical portion in the similar objects, and that its brain-tract is energetically operative, without, however, being sufficiently isolable in its activity as to stand out per se, and form the condition of a distinctly discriminated 'abstract idea.' We cannot even by careful search see the bridge over which we passed from the heart of one representation of that of the next. In some brains, however, this mode of transition is extremely common. It would be one of the most important of physiological discoveries could we assign the mechanical or chemical difference which makes the thoughts of one brain cling close to impartial redintegration, while those of another shoot about in all the lawless revelry of similarity. Why, in these latter brains, action should tend to focalize itself in small spots, while in the others it fills patiently its broad bed, it seems impossible to guess. Whatever the difference may be, it is what separates the man of genius from the prosaic creature of habit and routine thinking. In Chapter XXII we shall need to recur again to this point.

ASSOCIATION IN VOLUNTARY THOUGHT.

Hitherto we have assumed the process of suggestion of one object by another to be spontaneous. The train of imagery wanders at its own sweet will, now trudging in sober grooves of habit, now with a hop, skip, and jump darting across the whole field of time and space. This is revery, or musing; but great segments of the flux of our ideas consist of something very different from this. They are guided by a distinct purpose or conscious interest. As the Germans say, we nachdenken, or think towards a certain end. It is now necessary to examine what modification is made in the trains of our imagery by the having of an end in view. The course of our ideas is then called voluntary.

Physiologically considered, we must suppose that a purpose means the persistent activity of certain rather definite brain-processes throughout the whole course of thought. Our most usual cogitations are not pure reveries, absolute driftings, but revolve about some central interest or topic to which most of the images are relevant, and towards which we return promptly after occasional digressions. This interest is subserved by the persistently active brain-tracts we have supposed. In the mixed associations which we have hitherto studied, the parts of each object which form the pivots on which our thoughts successively turn have their interest largely determined by their connection with some general interest which for the time has seized upon the mind. If we call Z the brain-tract of general interest, then, if the object abc turns up, and b has more associations with Z than have either a or c, b will become the object's interesting, pivotal portion, and will call up its own associates exclusively. For the energy of b's brain-tract will be augmented by Z's activity, -- an activity which, from lack of previous connection between Z and a or c, does not influence a or c. If, for instance, I think of Paris whilst I am hungry, I shall not improbably find that its restaurants have become the pivot of my thought, etc., etc.

But in the theoretic as well as in the practical life there are interests of a more acute sort, taking the form of definite images of some achievement, be it action or acquisition, which we desire to effect. The train of ideas arising under the influence of such an interest constitutes usually the thought of the means by which the end shall be attained. If the end by its simple presence does not instantaneously suggest the means, the search for the latter becomes an intellectual problem. The solution of problems is the most characteristic and peculiar sort of voluntary thinking. Where the end thought of is some outward deed or gain, the solution is largely composed of the actual motor processes, walking, speaking, writing, etc., which lead up to it. Where the end is in the first instance only ideal, as in laying out a place of operations, the steps are purely imaginary. In both of these cases the discovery of the means may form a new sort of end, of an entirely peculiar nature, an end, namely, which we intensely desire before we have attained it, but of the nature of which, even whilst most strongly craving it, we have no distinct imagination whatever. Such an end is a problem.

The same state of things occurs whenever we seek to recall something forgotten, or to state the reason for a judgment which we have made intuitively. The desire strains and presses in a direction which it feels to be right but towards a point which it is unable to see. In short, the absence of an item is a determinant of our representations quite as positive as its presence can ever be. The gap becomes no mere void, but what is called an aching void. If we try to explain in terms of brain-action how a thought which only potentially exists can yet be effective, we seem driven to believe that the brain-tract thereof must actually be excited, but only in a minimal and sub-conscious way. Try for instance, to symbolize what goes on in a man who is racking his brains to remember a thought which occurred to him last week. The associates of the thought are there, many of them at least, but they refuse to awaken the thought itself. We cannot suppose that they do not irradiate at all into its brain-tract, because his mind quivers on the very edge of its recovery. Its actual rhythm sounds in his ears; the words seem on the imminent point of following, but fail. What it is that blocks the discharge and keeps the brain-excitement here from passing beyond the nascent into the vivid state cannot be guessed. But we see in the philosophy of desire and pleasure, that such nascent excitements, spontaneously tending to a crescendo, but inhibited or checked by other causes, may become potent mental stimuli and determinants of desire. All questioning, wonder, emotion of curiosity, must be referred to cerebral causes of some such form as this. The great difference between the effort to recall things forgotten and the search after the means to a given end, is that the latter have not, whilst the former have, already formed a part of our experience. If we first study the mode of recalling a thing forgotten, we can take up with better understanding the voluntary quest of the unknown.

The forgotten thing is felt by us as a gap in the midst of certain other things. If it is a thought, we possess a dim idea of where we were and what we were about when it occurred to us. We recollect the general subject to which it relates. But all these details refuse to shoot together into a solid whole, for the lack of the vivid traits of this missing thought, the relation whereof to each detail forms now the main interest of the latter. We keep running over the details in our mind, dissatisfied, craving something more. From each detail there radiate lines of association forming so many tentative guesses. Many of these are immediately seen to be irrelevant, are therefore void of interest, and lapse immediately from consciousness. Others are associated with the other details present, and with the missing thought as well. When these surge up, we have a peculiar feeling that we are 'warm,' as the children say when they play hide and seek; and such associates as these we clutch at and keep before the attention. Thus we recollect successively that when we had the thought in question we were at the dinner-table; then that of our friend J. D. was there; then that the subject talked about was so and so; finally, that the thought came à propos of a certain anecdote, and then that it had something to do with a French quotation. Now all these added associations arise independently of the will, by the spontaneous process we know so well. All that the will does is to emphasize and linger over those which seem pertinent, and ignore the rest. Through this hovering of the attention in the neighborhood of the desired object, the accumulation of associates becomes so great that the combined tensions of their neural processes break through the bar, and the nervous wave pours into the tract which has so long been awaiting its advent. And as the expectant, sub-conscious itching there, bursts into the fulness of vivid feeling, the mind finds an inexpressible relief.

The whole process can be rudely symbolized in a diagram. Call the forgotten thing Z, the first facts with which we felt it was related, a, b, and c, and the details finally operative in calling it up, l, m, and n. Each circle will then stand for the brain-process underlying the thought of the object denoted by the letter contained within it.

The activity in Z will at first be a mere tension; but as the activities in a, b, and c little by little irradiate into l, m, and n, and as all these processes are somehow connected with Z, their combined irradiations upon Z, represented by the centripetal arrows, succeed in helping the tension there to overcome the resistance, and in rousing Z also to full activity.

The tension present from the first in Z, even though it keep below the threshold of discharge, is probably to some degree co-operative with a, b, c in determining that l, m, n shall awake. Without Z's tension there might be a slower accumulation of objects connected with it. But, as aforesaid, the objects come before us through the brain's own laws, and the Ego of the thinker can only remain on hand, as it were, to recognize their relative values and brood over some of them, whilst others are let drop. As when we have lost a material object we cannot recover it by a direct effort, but only through moving about such neighborhoods wherein it is likely to lie, and trusting that it will then strike our eye; so here, by not letting our attention leave the neighborhood of what we seek, we trust that it will end by speaking to us of its own accord.[23]

Turn now to the case of finding the unknown means to a distinctly conceived end. The end here stands in the place of a, b, c, in the diagram. It is the starting-point of the irradiations of suggestion; and here, as in that case, what the voluntary attention does is only to dismiss some of the suggestions as irrelevant, and hold fast to others which are felt to be more pertinent -- let these be symbolized by l, m, n. These latter at last accumulate sufficiently to discharge all together into Z, the excitement of which process is, in the mental sphere, equivalent to the solution of our problem. The only difference between this case and the last, is that in this one there need be no original sub-excitement in Z, co-operating from the very first. When we seek a forgotten name, we must suppose the name's centre to be in a state of active tension from the very outset, because of that peculiar feeling of recognition which we get at the moment of recall. The plenitude of the thought seems here but a maximum degree of something which our mind divined in advance. It instantaneously fills a socket completely moulded to its shape; and it seems most natural to ascribe the identity of quality in our feeling of the gaping socket and our feeling of what comes to fill it, to the sameness of a nerve-tract excited in different degrees. In the solving of a problem, on the contrary, the recognition that we have found the means is much less immediate. Here, what we are aware of in advance seems to be its relations with the items we already know. It must bear a causal relation, or it must be an effect, or it must contain an attribute common to two items, or it must be a uniform concomitant, or what not. We know, in short, a lot about it, whilst as yet we have no knowledge of acquaintance with it (see p. 221), or in Mr. Hodgson's language, "we know what we want to find beforehand, in a certain sense, in its second intention, and do not know it, in another sense, in its first intention."[24] Our intuition that one of the ideas which turn up is, at last, our quœsitum, is due to our recognition that its relations are identical with those we had in mind, and this may be a rather slow act of judgment. In fact, every one knows that an object may be for some time present to his mind before its relations to other matters are perceived. To quote Hodgson again:

"The mode of operation is common to voluntary memory and reason.... But reasoning adds to memory the function of comparing or judging the images which arise.... Memory aims at filling the gap with an image which has at some particular time filled it before, reasoning with one which bears certain time-and space-relations to the images before and after" --

or, to use perhaps clearer language, one which stands in determinate logical relations to those data round about the gap which filled our mind at the start. This feeling of the blank form of relationship before we get the material quality of the thing related will surprise no one who has read Chapter IX.

From the guessing of newspaper enigmas to the plotting of the policy of an empire there is no other process than this. We trust to the laws of cerebral nature to present us spontaneously with the appropriate idea:

"Our only command over it is by the effort we make to keep the painful unfilled gap in consciousness.[25]... Two circumstances are important to notice: the first is, that volition has no power of calling up images, but only of rejecting and selecting from those offered by spontaneous redintegration.[26] But the rapidity with which this selection is made, owing to the familiarity of the ways in which spontaneous redintegration runs, gives the process of reasoning the appearance of evoking images that are foreseen to be conformable to the purpose. There is no seeing them before they are offered; there is no summoning them before they are seen. The other circumstance is, that every kind of reasoning is nothing, in its simplest form, but attention."[27]

It is foreign to our purpose here to enter into any detailed analysis of the different classes of mental pursuit. In a scientific research we get perhaps as rich an example as can be found. The inquirer starts with a fact of which he seeks the reason, or with an hypothesis of which he seeks the proof. In either case he keeps turning the matter incessantly in his mind until, by the arousal of associate upon associate, some habitual, some similar, one arises which he recognizes to suit his need. This, however, may take years. No rules can be given by which the investigator may proceed straight to his result; but both here and in the case of reminiscence the accumulation of helps in the way of associations may advance more rapidly by the use of certain routine methods. In striving to recall a thought, for example, we may of set purpose run through the successive classes of circumstances with which it may possibly have been connected, trusting that when the right member of the class has turned up it will help the thought's revival. Thus we may run through all the places in which we may have had it. We may run through the persons whom we remember to have conversed with, or we may call up successively all the books we have lately been reading. If we are trying to remember a person we may run through a list of streets or of professions. Some item out of the lists thus methodically gone over will very likely be associated with the fact we are in need of, and may suggest it or help to do so. And yet the item might never have arisen without such systematic procedure. In scientific research this accumulation of associates has been methodized by Mill under the title of 'The Four Methods of Experimental Inquiry.' By the 'method of agreement,' by that of 'difference,' by those of 'residues' and 'concomitant variations' (which cannot here be more nearly defined), we make certain lists of cases; and by ruminating these lists in our minds the cause we seek will be more likely to emerge. But the final stroke of discovery is only prepared, not effected, by them. The brain-tracts must, of their own accord, shoot the right way at last, or we shall still grope in darkness. That in some brains the tracts do shoot the right way much oftener than in others, and that we cannot tell why, -- these are ultimate facts to which we must never close our eyes. Even in forming our lists of instances according to Mill's methods, we are at the mercy of the spontaneous workings of Similarity in our brain. How are a number of facts, resembling the one whose cause we seek, to be brought together in a list unless the one will rapidly suggest the other through association by similarity?

SIMILARITY NO ELEMENTARY LAW.

Such is the analysis I propose, first of the three main types of spontaneous association, and then of voluntary association. It will be observed that the object called up may bear any logical relation whatever to the one which suggested it. The law requires only that one condition should be fulfilled. The fading object must be due to a brain-process some of whose elements awaken through habit some of the elements of the brain-process of the object which comes to view. This awakening is the operative machinery, the causal agency, throughout, quite as much so in the kind of association I have called by the name of Similarity, as in any other sort. The similarity between the objects, or between the thoughts (if similarity there be between these latter), has no causal agency in carrying us from one to the other. It is but a result -- the effect of the usual causal agent when this happens to work in a certain particular and assignable way. But ordinary writers talk as if the similarity of the objects were itself an agent, co-ordinate with habit, and independent of it, and like it able to push objects before the mind. This is quite unintelligible. The similarity of two things does not exist till both things are there -- it is meaningless to talk of it as an agent of production of anything, whether in the physical or the psychical realms.[28] It is a relation which the mind perceives after the fact, just as it may perceive the relations of superiority, of distance, of causality, of container and content, of substance and accident, or of contrast, between an object and some second object which the associative machinery calls up.[29]

There are, nevertheless, able writers who not only insist on preserving association by similarity as a distinct elementary law, but who make it the most elementary law, and seek to derive contiguous association from it. Their reasoning is as follows: When the present impression A awakens the idea b of its past contiguous associate B, how can this occur except through first reviving an image a of its own past occurrence. This is the term directly connected with b; so that the process instead of being simply A -- b is A -- a -- b. Now A and a are similars; therefore no association by contiguity can occur except through a previous association by similarity. The most important supposition here made is that every impression on entering the mind must needs awaken an image of its past self, in the light of which it is 'apperceived' or understood, and through the intermediation of which it enters into relation with the mind's other objects. This assumption is almost universally made; and yet it is hard to find any good reason for it. It first came before us when we were reviewing the facts of aphasia and mental blindness (see p. 50 ff.). But we then saw no need of optical and auditory images to interpret optical and auditory sensations by. On the contrary, we agreed that auditory sensations were understood by us only so far as they awakened non-auditory images, and optical sensations only so far as they awakened non-optical images. In the chapters on Memory, on Reasoning, and on Perception the same assumption will meet us again, and again will have to be rejected as groundless. The sensational process A and the ideational process a probably occupy essentially the same tracts. When the outer stimulus comes and those tracts vibrate with the sensation A, they discharge as directly into the paths which lead to B as when there is no outer stimulus and they only vibrate with the idea a. To say that the process A can only reach these paths by the help of the weaker process a is like saying that we need a candle to see the sun by. A replaces a, does all that a does and more; and there is no intelligible meaning, to my mind, in saying that the weaker process coexists with the stronger. I therefore consider that these writers are altogether wrong. The only plausible proof they give of the coexistence of a with A is when A gives us a sense of familiarity but fails to awaken any distinct thought of past contiguous associates. In a later chapter I shall consider this case. Here I content myself with saying that it does not seem conclusive as to the point at issue; and that I still believe association of coexistent or sequent impressions to be the one elementary law.

CONTRAST has also been held to be an independent agent in association. But the reproduction of an object contrasting with one already in the mind is easily explained on our principles. Recent writers, in fact, all reduce it either to similarity or contiguity. Contrast always presupposes generic similarity; it is only the extremes of a class which are contrasted, black and white, not black and sour, or white and prickly. A machinery which reproduces a similar at all, may reproduce the opposite similar, as well as any intermediate term. Moreover, the greater number of contrasts are habitually coupled in speech, young and old, life and death, rich and poor, etc., and are, as Dr. Bain says, in everybody's memory.[30]

I trust that the student will now feel that the way to a deeper understanding of the order of our ideas lies in the direction of cerebral physiology. The elementary process of revival can be nothing but the law of habit. Truly the day is distant when physiologists shall actually trace from cell-group to cell-group the irradiations which we have hypothetically invoked. Probably it will never arrive. The schematism we have used is, moreover, taken immediately from the analysis of objects into their elementary parts, and only extended by analogy to the brain. And yet it is only as incorporated in the brain that such a schematism can represent anything causal. This is, to my mind, the conclusive reason for saying that the order of presentation of the mind's materials is due to cerebral physiology alone.

The law of accidental prepotency of certain processes over others falls also within the sphere of cerebral probabilities. Granting such instability as the brain-tissue requires, certain points must always discharge more quickly and strongly than others; and this prepotency would shift its place from moment to moment by accidental causes, giving us a perfect mechanical diagram of the capricious play of similar association in the most gifted mind. The study of dreams confirms this view. The usual abundance of paths of irradiation seems, in the dormant brain, reduced. A few only are pervious, and the most fantastic sequences occur because the currents run -- 'like sparks in burnt-up paper' -- wherever the nutrition of the moment creates an opening, but nowhere else.

The effects of interested attention and volition remain. These activities seem to hold fast to certain elements, and by emphasizing them and dwelling on them, to make their associates the only ones which are evoked. This is the point at which an anti-mechanical psychology must, if anywhere, make it stand in dealing with association. Everything else is pretty certainly due to cerebral laws. My own opinion on the question of active attention and spiritual spontaneity is expressed elsewhere. But even though there be a mental spontaneity, it can certainly not create ideas or summon them ex abrupto. Its power is limited to selecting amongst those which the associative machinery has already introduced or tends to introduce. If it can emphasize, reinforce, or protract for a second either one of these, it can do all that the most eager advocate of free will need demand; for it then decides the direction of the next associations by making them hinge upon the emphasized term; and determining in this wise the course of the man's thinking, it also determines his acts.

THE HISTORY OF OPINION CONCERNING ASSOCIATION.

may be briefly glanced at ere we end the chapter.[31] Aristotle seems to have caught both the facts and the principle of explanation; but he did not expand his views, and it was not till the time of Hobbes that the matter was again touched on in a definite way. Hobbes first formulated the problem of the succession of our thoughts. He writes in Leviathan, chapter III, as follows:

"By consequence, or train of thoughts, I understand that succession of one thought to another which is called, to distinguish it from discourse in words, mental discourse. When a man thinketh on anything whatsoever, his next thought after is not altogether so casual as it seems to be. Not every thought to every thought succeeds indifferently. But as we have no imagination, whereof we have not formerly had sense, in whole or in parts; so we have no transition from one imagination to another, whereof we never had the like before in our senses. The reason whereof is this. All fancies are motions within us, relics of those made in the sense: and those motions that immediately succeeded one another in the sense continue also together after sense: insomuch as the former coming again to take place, and be predominant, the latter followeth, by coherence of the matter moved, in such manner, as water upon a plane table is drawn which way any one part of it is guided by the finger. But because in sense, to one and the same thing perceived, sometimes one thing, sometimes another succeedeth, it comes to pass in time that, in the imagining of anything, there is no certainty what we shall imagine next; only this is certain, it shall be something that succeeded the same before, at one time or another. This train of thoughts, or mental discourse, is of two sorts. The first is unguided, without design, and inconstant; wherein there is no passionate thought, to govern and direct those that follow, to itself, as the end and scope of some desire, or other passion.... The second is more constant; as being regulated by some desire and design. For the impression made by such things as we desire, or fear, is strong and permanent, or, if it cease for a time, of quick return: so strong is it, sometimes, as to hinder and break our sleep. From desire ariseth the thought of some means we have seen produce the like of that which we aim at; and from the thought of that, the thought of means to that mean; and so continually, till we come to some beginning within our own power. And because the end, by the greatness of the impression, comes often to mind, in case our thoughts begin to wander, they are quickly again reduced into the way: which observed by one of the seven wise men, made him give men this precept, which is now worn out, Respice finem; that is to say, in all your actions, look often upon what you would have, as the thing that directs all your thoughts in the way to attain it.

"The train of regulated thoughts is of two kinds; one, when of an effect imagined we seek the causes, or means that produce it: and this is common to man and beast. The other is, when imagining anything whatsoever, we seek all the possible effects that can by it be produced; that is to say, we imagine what we can do with it, when we have it. Of which I have not at any time seen any sign, but in man only; for this is a curiosity hardly incident to the nature of any living creature that has no other passion but sensual, such as are hunger, thirst, lust, and anger. In sum, the discourse of the mind, when it is governed by design, is nothing but seeking, or the faculty of invention, which the Latins called sagacitas, and sollertia; a hunting out of the causes, of some effect, present or past; or of the effects, of some present or past cause."

The most important passage after this of Hobbes is Hume's:

"As all simple ideas may be separated by the imagination, and may be united again in what form it pleases, nothing would be more unaccountable than the operations of that faculty, were it not guided by some universal principles, which render it, in some measure, uniform with itself in all times and places. Were ideas entirely loose and unconnected, chance alone would join them; and 'tis impossible the same simple ideas should fall regularly into complex ones (as they commonly do) without some bond of union among them, some associating quality, by which one idea naturally introduces another. This uniting principle among ideas is not to be considered as an inseparable connection; for that has been already excluded from the imagination. Nor yet are we to conclude that without it the mind cannot join two ideas; for nothing is more free than that faculty: but we are only to regard it as a gentle force, which commonly prevails, and is the cause why, among other things, languages so nearly correspond to each other; nature in a manner pointing to every one those simple ideas which are most proper to be united in a complex one. The qualities from which this association arises, and by which the mind is after this manner conveyed from one idea to another, are three, viz., RESEMBLANCE, CONTIGUITY in time or place, and CAUSE and EFFECT.

"I believe it will not be very necessary to prove that these qualities produce an association among ideas, and upon the appearance of one idea naturally introduce another. 'Tis plain that in the course of our thinking, and in the constant revolution of our ideas, our imagination runs easily from one idea to any other that resembles it, and that this quality alone is to the fancy a sufficient bond and association. 'Tis likewise evident, that as the senses, in changing their objects, are necessitated to change them regularly, and take them as they lie contiguous to each other, the imagination must by long custom acquire the same method of thinking, and run along the parts of space and time in conceiving its objects. As to the connection that is made by the relation of cause and effect, we shall have occasion afterwards to examine it to the bottom, and therefore shall not at present insist upon it. 'Tis sufficient to observe that there is no relation which produces a stronger connection in the fancy, and makes one idea more readily recall another, that the relation of cause and effect betwixt their objects.... These are therefore the principles of union or cohesion among our simple ideas, and in the imagination supply the place of that inseparable connection by which they are united in our memory. Here is a kind of ATTRACTION, which in the mental world will be found to have as extraordinary effects as in the natural, and to show itself in as many and as various forms. Its effects are everywhere conspicuous; but as to its causes, they are mostly unknown, and must be resolved into original qualities of human nature, which I pretend not to explain."[32]

Hume did not, however, any more than Hobbes, follow out the effects of which he speaks, and the task of popularizing the notion of association and making an effective school based on association of ideas alone was reserved for Hartley[33] and James Mill.[34] These authors traced minutely the presence of association in all the cardinal notions and operations of the mind. The several 'faculties' of the Mind were dispossessed; the one principle of association between ideas did all their work. As Priestley says:

"Nothing is requisite to make any man whatever he is, but a sentient principle with this single law.... Not only all our intellectual pleasures and pains but all the phenomena of memory, imagination, volition, reasoning and every other mental affection and operation, are but different modes or cases of the association of ideas."[35]

An eminent French psychologist, M. Ribot, repeats Hume's comparison of the law of association with that of gravitation, and goes on to say:

"It is remarkable that this discovery was made so late. Nothing is simpler, apparently, than to notice that this law of association is the truly fundamental, irreducible phenomenon of our mental life; that it is at the bottom of all our acts; that is permits of no exception; that neither dream, revery, mystic ecstasy, nor the most abstract reasoning can exist without it; that its suppression would be equivalent to that of thought itself. Nevertheless no ancient author understood it, for one cannot seriously maintain that a few scattered lines in Aristotle and the Stoics constitute a theory and clear view of the subject. It is to Hobbes, Hume, and Hartley that we must attribute the origin of these studies on the connection of our ideas. The discovery of the ultimate law of our psychologic acts has this, then, in common with many other discoveries: it came late and seems so simple that it may justly astonish us.

"Perhaps it is not superfluous to ask in what this manner of explanation is superior to the current theory of Faculties.[36] The most extended usage consists, as we know, in dividing intellectual phenomena into classes, in separating those which differ, in grouping together those of the same nature and in giving to these a common name and in attributing them to the same cause; it is thus that we have come to distinguish those diverse aspects of intelligence which are called judgment, reasoning, abstraction, perception, etc. This method is precisely the one followed in Physics, where the words caloric, electricity, gravity, designate the unknown causes of certain groups of phenomena. If one thus never forgets that the diverse faculties are only the unknown causes of known phenomena, that they are simply a convenient means of classifying the facts and speaking of them, if one does not fall into the common fault of making out of them substantial entities, creations which now agree, now disagree, so forming in the intelligence a little republic; then, we can see nothing reprehensible in this distribution into faculties, conformable as it is to the rules of a sound method and of a good natural classification. In what then is Mr. Bain's procedure superior to the method of the faculties? It is that the latter is simply a classification while his is an explanation. Between the psychology which traces intellectual facts back to certain faculties, and that which reduces them to the single law of association, there is, according to our way of thinking, the same difference that we find in Physics between those who attribute its phenomena to five or six causes, and those who derive gravity caloric, light, etc., from motion. The system of the faculties explains nothing because each one of them is only a flatus vocis which is of value merely through the phenomena which it contains, and signifies nothing more than these phenomena. The new theory, on the contrary, shows that the different processes of intelligence are only diverse cases of a single law; that imagination, deduction, induction, perception, etc., are but so many determinate ways in which ideas may combine with each other; and that the differences of faculties are only differences of association. It explains all intellectual facts, certainly not after the manner of Metaphysics which demands the ultimate and absolute reason of things; but after the manner of Physics which seeks only their secondary and immediate cause."[37]

The inexperienced reader may be glad of a brief indication of the manner in which all the different mental operations may be conceived to consist of images of sensation associated together.

Memory is the association of a present image with others known to belong to the past. Expectation the same, with future substituted for past. Fancy, the association of images without temporal order.

Belief in anything not present to sense is the very lively, strong, and steadfast association of the image of that thing with some present sensation, so that as long as the sensation persists the image cannot be excluded from the mind.

Judgment is 'transferring the idea of truth by association from one proposition to another that resembles it.'[38]

Reasoning is the perception that "whatever has any mark has that which it is a mark of"; in the concrete case the mark or middle term being always associated with each of the other terms and so serving as a link by which they are themselves indirectly associated together. This same kind of transfer of a sensible experience associated with another to a third also associated with that other, serves to explain emotional facts. When we are pleased or hurt we express it, and the expression associates itself with the feeling. Hearing the same expression from another revives the associated feeling, and we sympathize, i.e. grieve or are glad with him.

The other social affections, Benevolence, Conscientiousness, Ambition, etc., arise in like manner by the transfer of the bodily pleasure experienced as a reward for social service, and hence associated with it, to the act of service itself, the link of reward being dropped out. Just so Avarice when the miser transfers the bodily pleasures associated with the spending of money to the money itself, dropping the link of spending.

Fear is a transfer of the bodily hurt associated by experience with the thing feared, to the thought of the thing, with the precise features of the hurt left out. Thus we fear a dog without distinctly imagining his bite.

Love is the association of the agreeableness of certain sensible experiences with the idea of the object capable of affording them. The experiences themselves may cease to be distinctly imagined after the notion of their pleasure has been transferred to the object, constituting love there-for.

Volition is the association of ideas of muscular motion with the ideas of those pleasures which the motion produces. The motion at first occurs automatically and results in a pleasure unforeseen. The latter becomes so associated with the motion that whenever we think of it the idea of the motion arises; and the idea of the motion when vivid causes the motion to occur. This is an act of will.

Nothing is easier than for a philosopher of this school to explain from experience such a notion as that of infinitude.

"He sees in it an ordinary manifestation of one of the laws of the association of ideas, -- the law that the idea of a thing irresistibly suggests the idea of any other thing which has been often experienced in close conjunction with it, and not otherwise. As we have never had experience of any point of space without other points beyond it, nor of any point of time without others following it, the law of indissoluble association makes it impossible for us to think of any point of space or time, however distant, without having the idea irresistibly realized, in imagination, of other points still more remote. And thus the supposed original and inherent property of these two ideas is completely explained and accounted for by the law of association; and we are enabled to see that if Space or Time were really susceptible of termination, we should be just as unable as we now are to conceive the idea."[39]

These examples of the Associationist Psychology are with the exception of the last, very crudely expressed, but they suffice for our temporary need. Hartley and James Mill[40] improved upon Hume so far as to employ but a single principle of association, that of contiguity or habit. Hartley ignores resemblance, James Mill expressly repudiates it in a passage which is assuredly one of the curiosities of literature:

"I believe it will be found that we are accustomed to see like things together. When we see a tree, we generally see more trees than one; a sheep, more sheep than one; a man, more men than one. From this observation, I think, we may refer resemblance to the law of frequency [i.e., contiguity], of which it seems to form only a particular case."

Mr. Herbert Spencer has still more recently tried to construct a Psychology which ignores Association by Similarity,[41] and in a chapter, which also is a curiosity, he tries to explain the association of two ideas by a conscious reference of the first to the point of time when its sensation was experienced, which point of time is no sooner thought of than its content, namely, the second idea, arises. Messrs. Bain and Mill, however, and the immense majority of contemporary psychologists retain both Resemblance and Contiguity as irreducible principles of Association.

Professor Bain's exposition of association is by common consent looked upon as the best expression of the English school. Perception of agreement and difference, retentiveness, and the two sorts of association, contiguity and similarity, are by him regarded as constituting all that is meant by intellect proper. His pages are painstaking and instructive from a descriptive point of view; though, after my own attempt to deal with the subject causally, I can hardly award to them any profound explanatory value. Association by Similarity, too much neglected by the British school before Bain, receives from him the most generous exemplification. As an instructive passage, the following, out of many equally good, may be chosen to quote:

"We may have similarity in form with diversity of use, and similarity of use with diversity of form. A rope suggests other ropes and cords, if we look to the appearance; but looking to the use, it may suggest an iron cable, a wooden prop, an iron girding, a leather band, or bevelled gear. In spite of diversity of appearance, the suggestion turns on what answers a common end. If we are very much attracted by sensible appearances, there will be the more difficulty in recalling things that agree only in the use; if, on the other hand, we are profoundly sensitive to the one point of practical efficiency as a tool, the peculiarities not essential to this will be little noticed, and we shall be ever ready to revive past objects corresponding in use to some one present, although diverse in all other circumstances. We become oblivious to the difference between a horse, a steam-engine, and a waterfall, when our minds are engrossed with the one circumstance of moving power. The diversity in these had no doubt for a long time the effect of keeping back their first identification; and to obtuse intellects, this identification might have been for ever impossible. A strong concentration of mind upon the single peculiarity of mechanical force, and a degree of indifference to the general aspect of the things themselves, must conspire with the intellectual energy of resuscitation by similars, in order to summon together in the view three structures so different. We can see, by an instance like this, how new adaptations of existing machinery might arise in the mind of a mechanical inventor. When it first occurred to a reflecting mind that moving water had a property identical with human or brute force, namely, the property of setting other masses in motion, overcoming inertia and resistance, -- when the sight of the stream suggested through this point of likeness the power of the animal, -- a new addition was made to the class of prime movers, and when circumstances permitted, this power could become a substitute for the others. It may seem to the modern understanding, familiar with water-wheels and drifting rafts, that the similarity here was an extremely obvious one. But if we put ourselves back into an early state of mind, when running water affected the mind by its brilliancy, its roar, and irregular devastation, we may easily suppose that to identify this with animal muscular energy was by no means an obvious effect. Doubtless when a mind arose, insensible by natural constitution to the superficial aspects of things, and having withal a great stretch of identifying intellect, such a comparison would then be possible. We may pursue the same example one stage further, and come to the discovery of steam power, or the identification of expanding vapor with the previously known sources of mechanical force. To the common eye, for ages, vapor presented itself as clouds in the sky; or as a hissing noise at the spout of a kettle, with the formation of a foggy curling cloud at a few inches' distance. The forcing up of the lid of a kettle may also have been occasionally observed. But how long was it ere any one was struck with the parallelism of this appearance with a blast of wind, a rush of water, or an exertion of animal muscle? The discordance was too great to be broken through by such a faint and limited amount of likeness. In one mind, however, the identification did take place, and was followed out into its consequences. The likeness had occurred to other minds previously, but not with the same results. Such minds must have been in some way or other distinguished above the millions of mankind; and we are now endeavoring to give the explanation of their superiority. The intellectual character of Watt contained all the elements preparatory to a great stroke of similarity in such a case; -- a high susceptibility, both by nature and by education, to the mechanical properties of bodies; ample previous knowledge or familiarity; and indifference to the superficial and sensational effects of things. It is not only possible, however, but exceedingly probable, that many men possessed all these accomplishments; they are of a kind not transcending common abilities. They would in some degree attach to a mechanical education almost as a matter of course. That the discovery was not sooner made supposes that something farther, and not of common occurrence, was necessary; and this additional endowment appears to be the identifying power of Similarity in general; the tendency to detect likeness in the midst of disparity and disguise. This supposition accounts for the fact, and is consistent with the known intellectual character of the inventor of the steam-engine."[42]

Dr. Hodgson's account of association is by all odds the best yet propounded in English.[43] All these writers hold more or less explicitly to the notion of atomistic 'ideas' which recur. In Germany, the same mythological supposition has been more radically grasped, and carried out to a still more logical, if more repulsive, extreme, by Herbart[44] and his followers, who until recently may be said to have reigned almost supreme in their native country.[45] For Herbart each idea is a permanently existing entity, the entrance whereof into consciousness is but an accidental determination of its being. So far as it succeeds in occupying the theatre of consciousness, it crowds out another idea previously there. This act of inhibition gives it, however, a sort of hold on the other representation which on all later occasions facilitates its following the other into the mind. The ingenuity with which most special cases of association are formulated in this mechanical language of struggle and inhibition, is great, and surpasses in analytic thoroughness anything that has been done by the British school. This, however, is a doubtful merit, in a case where the elements dealt with are artificial; and I must confess that to my mind there is something almost hideous in the glib Herbartian jargon about Vorstellungsmassen and their Hemmungen and Hemmungssummen, and sinken and erheben and schweben, and Verschmelzungen and Complexionen. Herr Lipps, the most recent systematic German Psychologist, has, I regret to say, carried out the theory of ideas in a way which the great originality, learning, and acuteness he shows make only the more regrettable.[46] Such elaborately artificial constructions are, it seems to me, only a burden and a hindrance, not a help, to our science.[47]

In French, M. Rabier in his chapter on Association,[48] handles the subject more vigorously and acutely than any one. His treatment of it, though short, seems to me for general soundness to rank second only to Hodgson's.

In the last chapter we already invoked association to account for the effect of use in improving discrimination. In later chapters we shall see abundant proof of the immense part which it plays in other processes, and shall then readily admit that few principles of analysis, in any science, have proved more fertile than this one, however vaguely formulated it often may have been. Our own attempt to formulate it more definitely, and to escape the usual confusion between causal agencies and relations merely known, must not blind us to the immense services of those by whom the confusion was unfelt. From this practical point of view it would be a true ignoratio elenchi to flatter one's self that one has dealt a heavy blow at the psychology of association, when one has exploded the theory of atomistic ideas, or shown that contiguity and similarity between ideas can only be there after association is done.[49] The whole body of the associationist psychology remains standing after you have translated 'ideas' into 'objects,' on the one hand, and 'brain-processes' on the other; and the analysis of faculties and operations is as conclusive in these terms as in those traditionally used.

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Footnotes

[1] The theory propounded in this chapter, and a good many pages of the text, were originally published in the Popular Science Monthly for March, 1880.

[2] Compare Renouvier's criticism of associationism in his Essais de Critique générale, Logique, II. p. 493 foll.

[3] Unless the name belong to a rapidly uttered sentence, when no substantive image may have time to arise.

[4] In his observations he says that time was lost in mentally taking in the word which was the cue, "owing to the quiet unobtrusive way in which I found it necessary to bring it into view, so as not to distract the thoughts. Moreover, a substantive standing by itself is usually the equivalent of too abstract an idea for us to conceive properly without delay. Thus it is very difficult to get a quick conception of the word 'carriage,' because there are so many different kinds -- two-wheeled, four-wheeled, open and closed, and in so many different possible positions, that the mind possibly hesitates amidst an obscure sense of many alterations that cannot blend together. But limit the idea to say a landau, and the mental association declares itself more quickly." (Inquiries, etc., p. 190.)

[5] Physiol. Psych., II. 280 fol.

[6] For interesting remarks on the sorts of things associated, in these experiments, with the prompting word, see Galton, op. cit. pp. 185-203, and Trautscholdt in Wundt's Psychologische Studien, I. 213.

[7] Mind, XI. 64-5.

[8] This value is much smaller than that got by Wundt as above. No reason for the difference is suggested by Mr. Cattell. Wundt calls attention to the fact that the figures found by him give an average, 0.720", exactly equal to the time interval which in his experiments (vide infra, chapter on Time) was reproduced without error either way, and to that required, according to the Webers, for the legs to swing in rapid locomotion. "It is not improbable," he adds, "that this psychic constant, of the mean association-time and of the most correct appreciation of a time-interval, may have been developed under the influence of the most usual bodily movements, which also have determined the manner in which we tend to subdivide rhythmically longer periods of time." (Physiol. Psch., II. 286). The rapprochement is of that tentative sort which it is no harm for psychologists to make, provided they recollect how very fictitious and incomparable mutually all these averages derived from different observers, working under different conditions, are. Mr. Cattell's figure throws Wundt's ingenious parallel entirely out of line. -- The only measurements of association-time which so far seem likely to have much theoretic importance are a few made on insane patients by Von Tschisch (Mendel's Neurologisches Centralblatt, 15 Mai, 1885, 3 Jhrg., p. 217). The simple reaction time was found about normal in three patients, one with progressive paralysis, one with inveterate mania of persecution, one recovering from ordinary mania. In the convalescent maniac and the paralytic, however, the association-time was hardly half as much as Wundt's normal figure (0.28" and 0.23" instead of 0.7' -- smaller also than Cattell's), whilst in the sufferer from delusions of persecution and hallucinations it was twice as great as normal (1.39" instead of 0.7"). This latter patient's time was six-fold that of the paralytic. Herr von Tschisch remarks on the connection of the short times with diminished power for clear and consistent processes of thought, and on that of the long times with the persistent fixation of the attention upon monotonous objects (delusions). Miss Marie Walitzky (Revue Philosophique, XXVIII. 583) has carried Von Tschisch's observations still farther, making 18,000 measurements in all. She found association-time increased in paralytic dementia and diminished in mania. Choice-time, on the contrary, is increased in mania.

[9] Mind, XII. 67-74.

[10] Compare Bain's law of Association by Contiguity: "Actions, Sensations, and States of Feeling, occurring together or in close succession, tend to grow together, or cohere, in such a way that, when any one of them is afterwards presented to the mind, the others are apt to be brought up in idea" (Senses and Intellect, p. 327). Compare also Hartley's formulation: "Any sensations A, B, C, etc., by being associated with one another a sufficient Number of Times, get such a power over the corresponding Ideas, a, b, c, etc., that any one of the sensations A, when impressed alone, shall be able to excite in the Mind b, c, etc., the ideas of the rest." (Observations on Man, part I. chap. I. § 2, Prop. X.) The statement in the text differs from these in holding fast to the objective point of view. It is things, and objective properties in things, which are associated in our thought.

[11] Encyclopædia Britannica, 9th Ed., article Psychology, p. 60, col. 2.

[12] Physiol. Psych., 2d ed. II. 300.

[13] The difficulty here as with habit überhaupt is in seeing how new paths come first to be formed (cf. above, 109). Experience shows that a new path is formed between centres for sensible impressions whenever these vibrate together or in rapid succession. A child sees a certain bottle and hears it called 'milk,' and thenceforward thinks the name when he again sees the bottle. But why the successive or simultaneous excitement of two centres independently stimulated from without, one by sight and the other by hearing, should result in a path between them, one does not immediately see. We can only make hypotheses. Any hypothesis of the specific mode of their formation which tallies well with the observed facts of association will be in so far forth credible, in spite of possible obscurity. Herr Münsterberg thinks (Beiträge zur exp. Psychologie, Heft 1, p. 132) that between centres excited successively from without no path ought to be formed, and that consequently all contiguous association is between simultaneous experiences. Mr. Ward (loc. cit.) thinks on the contrary, that it can only be between successive experiences: "The association of objects simultaneously presented can be resolved into an association of objects successively attended to.... It seems hardly possible to mention a case in which attention to the associated objects could not have been successive. In fact, an aggregate of objects on which attention could be focused at once would be already associated." Between these extreme possibilities, I have refrained from deciding in the text, and have described contiguous association as holding between both successively and coexistently presented objects. The physiological question as to how we may conceive the paths to originate had better be postponed till it comes to us again in the chapter on the Will, where we can treat it in a broader way. It is enough here to have called attention to it as a serious problem.

[14] Essay, bk. II. chap. XXXIII. § 6. Compare Hume, who, like Locke, only uses the principle to account for unreasonable and obstructive mental associations:

"'Twould have been easy to have made an imaginary dissection of the brain, and have shown why, upon our conception of any idea, the animal spirits run into all the contiguous traces, and rouse up the other ideas that are related to it. But though I have neglected any advantage which I might have drawn from this topic in explaining the relations of ideas, I am afraid I must here have recourse to it, in order to account for the mistakes that arise from these relations. I shall therefore observe, that as the mind is endowed with a power of exciting any idea it pleases; whenever it dispatches the spirits into that region of the brain in which the idea is placed, these spirits always excite the idea, when they run precisely into the proper traces, and rummage that cell which belongs to the idea. But as their motion is seldom direct, and naturally turns a little to the one side or the other; for this reason the animal spirits, falling into the contiguous traces, present other related ideas in lieu of that which the mind desired at first to survey. This change we are not always sensible of; but continuing still the same train of thought, make use of the related idea which is presented to us, and employ it in our reasoning, as if it were the same with what we demanded. This is the cause of many mistakes and sophisms in philosophy; as will naturally be imagined, and as it would be easy to show, if there was occasion."

[15] Op. cit. prop. XI.

[16] See Chapter III, p. 82-5.

[17] I strongly advise the student to read his Senses and Intellect, pp. 544-556.

[18] Time and Space, p. 266. Compare Coleridge: "The true practical general law of association is this: that whatever makes certain parts of a total impression more vivid or distinct than the rest will determine the mind to recall these, in preference to others equally linked together by the common condition of contemporaeity or of contiguity. But the will itself, by confining and intensifying the attention, may arbitrarily give vividness or distinctness to any object whatsoever." (Biographia Litteraria, Chap. V.)

[19] Leviathan, pt. I. chap. III., init.

[20] I refer to a recency of a few hours. Mr. Galton found that experiences from boyhood and youth were more likely to be suggested by words seen at random than experiences of later years. See his highly interesting account of experiments in his Inquiries into Human Faculty, pp. 191-203.

[21] For other instances see Wahle, in Vierteljsch f. Wiss. Phil., IX. 144-417 (1885).

[22] I retain the title of association by similarity in order not to depart from common usage. The reader will observe, however, that my nomenclature is not based on the same principle throughout. Impartial redintegration connotes neural processes; similarity is an objective relation perceived by the mind; ordinary or mixed association is a merely denotative word. Total recall, partial recall, and focalized recall, of associates, would be better terms. But as the denotation of the latter word is almost identical with that of association by similarity, I think it better to sacrifice propriety to popularity, and to keep the latter well-worn phrase.

[23] No one has described this process better than Hobbes: "Sometimes a man seeks what he hath lost; and from that place and time wherein he misses it, his mind runs back from place to place and time to time to find where and when he had it; that is to say, to find some certain and limited time and place, in which to begin a method of seeking. Again, from thence his thoughts run over the same places and times to find what action or other occasion might make him lose it. This we call Remembrance, or calling to mind. Sometimes a man knows a place determinate, within the compass whereof he is to seek; and then his thoughts run over all the parts thereof, in the same manner as one would sweep a room to find a jewel, or as a spaniel ranges the field till he find a scent, or as a man should run over the alphabet to start a rhyme." (Leviathan, 165, p. 10.)

[24] Theory of Practice, vol. I. p. 394.

[25] Ibid. p. 394.

[26] All association is called redintegration by Hodgson.

[27] Ibid p. 400. Compare Bain, Emotions and Will, p. 377. "The outgoings of the mind are necessarily random; the end alone is the thing that is clear to the view, and with that there is a perception of the fitness of every passing suggestion. The volitional energy keeps up the attention on the active search: and the moment that anything in point rises before the mind, it springs upon that like a wild beast upon its prey."

[28] Compare what is said of the principle of Similarity by F. H. Bradley, Principles of Logic, pp. 294 ff.; E. Rabier, Psychologie, 187 ff.; Paulhan, Critique Philosophique, 2me Série, I. 458; Rabier, ibid. 460; Pillon, ibid. II. 55; B. P. Bowne, Introduction to Psych. Theory, 92; Ward, Encyclop. Britt. art. Psychology, p. 60; Wahle, Vierteljahrsch. f. wiss. Philos. IX. 426-431.

[29] Dr. McCosh is accordingly only logical when he sinks similarity in what he calls the "Law of Correlation, according to which, when we have discovered a relation between things, the idea of one tends to bring up the others" (Psychology, the Cognitive Powers, p. 130). The relations mentioned by this author are Identity, Whole and Parts, Resemblance, Space, Time, Quantity, Active Property, and Cause and Effect. If perceived relations among objects are to be treated as grounds for their appearance before the mind, similarity has of course no right to an exclusive, or even to a predominant, place.

[30] Cf. Bain, Senses and Intellect, 564 ff.; J. S. Mill, Note 39 to J. Mill's Analysis; Lipps, Grundtatsachen, 97.

[31] See, for farther details, Hamilton's Reid, Appendices D** and D***; and L. Ferri, La Psychologie de l'Association (Paris, 1883). Also Robertson, art. Association in Encyclop. Britannica.

[32] Treatise of Human Nature, part I. § IV.

[33] Observations on Man (London, 1749).

[34] Analysis of the Phenomena of the Human Mind (1829).

[35] Hartley's Theory, 2d ed. (1790) p. XXVII.

[36] [Current, that is, in France. -- W. J.]

[37] La Psychologie Anglaise, p. 242.

[38] Priestley, op. cit. p. XXX.

[39] Review of Bain's Psychology, by J. S. Mill, in Edinb. Review, Oct. 1, 1859, p. 293.

[40] Analysis of the Phenomena of the Human Mind, J. S. Mill's edition, vol. I. p. 111.

[41] On the Associability of Relations between Feelings, in Principles of Psychology, vol. I. p. 259. It is impossible to regard the "cohering of each feeling with previously-experienced feelings of the same class, order, genus, species, and, so far as may be, the same variety," which Spencer calls (p. 257) 'the sole process of association of feelings.' as any equivalent for what is commonly known as Association by similarity.

[42] The Senses and the Intellect, pp. 491-3.

[43] See his Time and Space, chapter V, and his Theory of Practice, §§ 53 to 57.

[44] Psychologie als Wissenschaft (1824), 2.

[45] Prof. Ribot, in chapter I of his 'Contemporary German Psychology,' has given a good account of Herbart and his school, and of Beneke, his rival and partial analogue. See also two articles on the Herbartian Psychology, by G. F. Stout, in Mind for 1888. J. D. Morrell's Outlines of Mental Philosophy (2d ed., London, 1862) largely follows Herbart and Beneke. I know of no other English book which does so.

[46] See his Grundtatsachen des Bewusstseins (1883), chap. VI et passim, especially pp. 106 ff., 364.

[47] The most burdensome and utterly gratuitous of them are perhaps Steinthal's, in his Einleitung in die Psychologie, 2te Aufl. (1881). Cf. also G. Glogau: Steinthal's Psychologische Formeln (1886).

[48] Leçons de Philosophie, I. Psychologie, chap. XVI (1884).

[49] Mr. F. H. Bradley seems to me to have been guilty of something very like this ignoratio elenchi in the, of course, subtle and witty but decidedly long-winded critique of the association of ideas, contained in book II. part II. chap. I. of his Principles of Logic.