Here we come to the doctrine which for him and his school gave the key to all psychological problems. It was James Mill's real merit, according to his son, that he carried the principle of association of ideas further than it had been carried by Hartley or other predecessors.[514] The importance of the doctrine, indeed, is implied in the very statement of the problem. If it be true, or so far as it is true, that our consciousness reveals to us simply a series of 'sensations' and 'ideas,' the question must be how they are combined. 'Thought succeeds thought, idea follows idea incessantly,'[515] says Mill; and this phrase assumes 'thoughts' and 'ideas' to be separable atoms. How, then, do they come to coalesce into an apparently continuous stream? The mind is a stream of 'ideas.' If the stream is composed of drops, we must, of course, consider the drops as composing the stream. The question is, What laws can we assign which will determine the process of composition? The phrase 'association' admittedly expresses some general and very familiar truths. Innumerable connections may be established when there is no assignable ground of connection in the ideas themselves other than the fact of a previous contact. One idea not only calls up the other, but in some way generates a belief in an independent connection. We hear thunder, for example, and think of lightning. The two ideas are entirely distinct and separate, for they are due to different senses. Yet we not only think of lightning when we hear thunder, but we have no doubt that there is a causal connection. We believe in this connection, again, though no further explanation can be given of the fact. Thunder and lightning have occurred together, and we infer that they will, and even must, occur together. When we examine our whole structure of belief, we find such 'arbitrary' associations pervade it in every direction. Language itself is learned simply by association. There is no connection whatever between the sound of the word 'man' and the 'ideas' which the word excites, beyond the fact that the sound has been previously heard when the ideas were excited. Here, then, is a phenomenon to be explained or generalised. We have in countless cases a certain connection established for which no further reason can be assigned than the fact of its previous occurrence. On such a ground, we believe that fire burns, that bread is wholesome, that stones fall; and but for such beliefs could know nothing of the outside world. 'Contingent' truth, therefore, or truth derived from mere contact, pervades, if it does not constitute, the whole fabric of our whole knowledge. To prove that all our knowledge is derived from experience is, according to Mill, to prove that in some sense or other association of ideas lies at the base of all intellectual processes. When Locke introduced a chapter upon 'Association of Ideas' into the fourth edition of his essay, he treated it as the exceptional case. Some ideas had a connection traceable by reason; others were only connected by 'chance and custom.' Association does not explain reasoning, only the deviations from reasoning. But with Hume and Hartley the relation is inverted. The principle, instead of being an exceptional case, is simply the universal rule from which logical connection may be deduced as a special case.
The facts upon which Mill relied, and the account of them which he gave, require notice and embodiment in any sound psychology. In some shape or other they form the starting-point of all later systems. Mill's vigorous application of his principle, worked out with imperfect appreciation and with many oversights, had therefrom, at least, the merit of preparing the ground for a more scientific method. In any case, however, his conclusions, so far as sound, must be placed in a different framework of theory. It becomes necessary to dwell chiefly upon the curious defects of his theory, if taken as he wished it to be taken, for an ultimate scientific statement. The fact that there is a synthesis and an analysis is expressed by 'association.' But what more can we say? What are the 'laws' of association? Unless some rule can be given, we shall get nothing that can be called a theory. One idea is not suggested by the other through any logical process. They are still 'conjoined' but not 'connected.' The connection, therefore, must be given by something different from the ideas themselves. Now the order of the original 'sensations' depends upon the 'objects of nature,' and is therefore left to 'physical philosophy.'[516] They occur, however, either in 'synchronous' or in 'successive' order. Then 'ideas' spring up in the order of 'sensations,' and this is the 'general law of association of ideas.'[517] The synchronous sensations produce synchronous ideas and the successive sensations successive ideas. Finally, the strength of the association between the ideas depends upon 'the vividness of the associated feelings, and the frequency of the association.'[518] Hume had said that association depended upon three principles, 'contiguity in time and place,' 'causation,' and 'resemblance.' Contiguity in time corresponds to the successive, and contiguity in place to the synchronous, order. Causation, as Brown had finally proved,[519] means simply antecedence and consequence. 'Resemblance' remains and is, as Mill afterwards says,[520] a most important principle; but in an unlucky moment he is half inclined to reduce even 'resemblance' to 'contiguity.'[521] Resemblance is, he even suggests, merely 'a case of frequency,' because we generally see like things together. When we see one tree or sheep, we generally see several trees or sheep. J. S. Mill mildly remarks upon this quaint suggestion as the 'least successful simplification' in the book. He argues the point gravely. Sheep, it is clear, are not seen to be like because they often compose a flock, but are considered to be a flock because they are seen to be like. To do James Mill justice, he drops the argument as soon as he has struck it out. It is only worth notice as showing his aim. 'Likeness' seems to imply a relation dependent on the ideas themselves; not purely external and arbitrary. If we could get rid of likeness, all association would ultimately be 'contiguity.' 'The fundamental law of association,' as he says elsewhere,[522] 'is that when two things have been frequently found together, we never perceive or think of the one without thinking of the other.' The two ideas are associated as two balls are associated when they are in the same box. So far as they are themselves concerned, they might be separated without any alteration in their own properties. What, then, corresponds to the 'box'? Association depends upon relations of time and space. Things are associated by occurring in succession or together; the red colour of a rose is in the same place with the shape of the leaf; the scent is perceived at the same time with the colour. The thunder follows the lightning. What, then, he might ask, are 'time' and 'space'? Are they 'ideas' or 'sensations' or qualities of the objects? or, in any case, as supplying the ultimate principle of association, do they not require investigation? Before coming to that problem, however, we have to settle other knotty points. We must clear away illusions which seem to introduce something more than association. Elements of thought not at first sight expressible simply in terms of sensations and ideas must be analysed to show that they are only disguises for different combinations of the facts. Reasoning, according to most logicians, supposes, first, concepts, and therefore some process of classification of the objects of thought; and, secondly, some process of combining these concepts to bring out hitherto unknown truths. What, then, is the meaning of the general or abstract symbols employed in the process? Mill's provision of raw materials consists so far of sensations and ideas, which are worked up so as to form 'clusters' (the word is taken from Hartley) and 'trains.' This corresponds to synchronous and successive associations. How does the logical terminology express these 'clusters' and 'trains'? Mill answers by a theory of 'naming.' Language fulfils two purposes; it is required in order to make our ideas known to others; and in order to fix our own ideas. Ideas are fluctuating, transitory, and 'come into the mind unbidden.' We must catch and make a note of these shifting crowds of impalpable entities. We therefore put marks upon the simple sensations or upon the 'clusters.' We ticket them as a tradesman tickets bundles of goods in his warehouse, and can refer to them for our own purposes or those of others. As the number of objects to be marked is enormous, as there are countless ideas and clusters and clusters of clusters of endless variety to be arranged in various ways, one main object of naming is economy. A single word has to be used to mark a great number of individuals. This will account for such general names as are represented by noun-substantives: man, horse, dog, and so forth. Mill then proceeds, with the help of Horne Tooke, to explain the other grammatical forms. An adjective is another kind of noun marking a cross division. Verbs, again, are adjectives marking other sets of facts, and enabling us to get rid of the necessity of using a new mark for every individual or conceivable combination into clusters. J. S. Mill remarks that this omits the special function of verbs—their 'employment in predication.'[523] James Mill, however, has his own view of 'predication.' 'Man' is a mark of John, Peter, Thomas, and the rest. When I say 'John is a man,' I mean that 'man is another mark to that idea of which John is a mark.'[524] I am then able to make a statement which will apply to all the individuals, and save the trouble of repeating the assertion about each. 'Predication,' therefore, is simply a substitution of one name for another. So, for example, arithmetic is simply naming. What I call two and two, I also call four. The series of thoughts in this case is merely 'a series of names applicable to the same thing and meaning the same thing.'[525] This doctrine, as J. S. Mill remarks, is derived from Hobbes, whom Leibniz in consequence called plus quam nominalis.[526] My belief that two and two make four explains why I give the same name to certain numbers; but the giving the name does not explain the belief. Meanwhile, if a class name be simply the mark which is put upon a bundle of things, we have got rid of a puzzle. Mill triumphs over the unfortunate realists who held that a class meant a mysterious entity, existing somewhere apart from all the individuals in which it is embodied. There is really nothing mysterious; a name is first the mark of an individual, the individual corresponding to a 'cluster' or a set of 'simple ideas, concreted into a complex idea.'[527] Then the name and the complex idea are associated reciprocally; each 'calls up' the other. The complex idea is 'associated' with other resembling ideas. The name becomes a talisman calling up the ideas of an indefinite number of resembling individuals, and the name applied to one in the first instance becomes a mark which calls up all, or, as he says, is the 'name of the whole combination.' Classification, therefore, 'is merely a process of naming, and is all resolvable into association.'[528] The peculiarity of this theory, as his commentators again remark, is that it expressly omits any reference to abstraction. The class simply means the aggregate of resembling individuals without any selection of the common attributes which are, in J. S. Mill's phrase, 'connoted' by the class-name. Abstraction, as James Mill explains, is a subsidiary process, corresponding to the 'formation of sub-species.'[529]
Mill has now shown how the various forms of language correspond to ideas, formed into clusters of various orders by the principle of association. The next step will naturally be to show how these clusters are connected in the process of reasoning. Here the difficulty about predication recurs. J. S. Mill[530] remarks that his father's theory of predication consistently omits 'the element Belief.' When I say, 'John is a man,' I make an affirmation or assert a belief. I do not simply mean to call up in the mind of my hearer a certain 'cluster' or two coincident clusters of ideas, but to convey knowledge of truths. The omission of reference to belief is certainly no trifle. Mill has classified the various ideas and combinations of ideas which are used in judgment, but the process of judgment itself seems to have slipped out of account. He may have given us, or be able to give us, a reasoned catalogue of the contents of our minds, but has not explained how the mind itself acts. It is a mere passive recipient of ideas, or rather itself a cluster of ideas cohering in various ways, without energy of its own. One idea, as he tells us, calls up another 'by its own associating power.'[531] Ideas are things which somehow stick together and revive each other, without reference to the mind in which they exist or which they compose. This explains his frequent insistence upon one assertion. As we approach the question of judgment he finds it essential. 'Having a sensation and having a feeling,' he says, 'are not two things.' To 'feel an idea and be conscious of that feeling are not two things; the feeling and the consciousness are but two names for the same thing.'[532] So, again, 'to have a sensation and to believe that we have it, are not distinguishable things.'[533] Locke's reflection thus becomes nothing but simple consciousness, and having a feeling is the same as attending to it.[534] The point is essential. It amounts to saying that we can speak of a thought as though it were simply a thing.
Thus belief not only depends upon, but actually is association. 'It is not easy,' he says, 'to treat of memory, belief, and judgment separately.'[535] As J. S. Mill naturally asks, 'How is it possible to treat of belief without including in it memory and judgment?' Memory is a case of belief, and judgment an 'act of belief.'[536] To James Mill, however, it appears that as these different functions all involve association, they may be resolved into varying applications of that universal power. Memory involves 'an idea of my present self' and an 'idea of my past self,' and to remember is to 'run over the intervening states of consciousness called up by association.'[537] Belief involves association at every step. The belief in external objects is, as 'all men admit' ... 'wholly resolvable into association.'[538] 'That a cause means and can mean nothing to the human mind but constant antecedence' (and therefore 'inseparable association,' as he thinks) 'is no longer a point in dispute.'[539] Association, it is true, may produce wrong as well as right beliefs; right beliefs when 'in conformity with the connections of things,'[540] and wrong beliefs when not in conformity. In both cases the belief is produced by 'custom,' though, happily, the right custom is by far the commonest. The 'strength of the association follows the frequency.' The crow flies east as well as west; but the stone always falls downwards.[541] Hence I form an 'inseparable association' corresponding to a belief in gravitation, but have no particular belief about the direction of a crow's flight.
This gives the doctrine of 'indissoluble association'—the pivot of the whole scheme—the doctrine, says J. S. Mill, which, 'if it can be proved, is the greatest of all the triumphs of the Association Philosophy.'[542] The younger Mill always insisted upon the vast importance of the principle; but he here admits a difficulty. In a long note[543] upon James Mill's chapter on 'Belief,' conspicuous for his usual candour, he confesses the inadequacy of his father's view. The comment indicates the point of divergence and yet shows curiously the ground common to both. James Mill's theory states facts in some sense undeniable. Our 'ideas' cohere and combine to form a tissue: an imagery or series of pictures which form the content and are somehow the ground of our beliefs. The process of formation clearly involves 'association.' The scent of the rose is associated with the colour: both with the visible form and so forth. But is this process the same thing as believing, or have we to explain the belief by some mental activity different from, however closely connected with, the imagination, or in his phrase the 'ideation'? Here J. S. Mill finds a difficulty. The statement, 'I believe that thunder will follow lightning,' is something more than the statement, 'the sight suggests or calls up the sound.' The mental picture considered by itself may be described as a fact, without considering what belief, or whether any belief, is implied. J. S. Mill therefore makes a distinction intended to clear up his father's confusion. There is a difference, he says, between remembering 'a real fact' and remembering a 'thought.'[544] He illustrates this by the difference between the idea of Lafayette and the idea of Falstaff. Lafayette was real, and had been seen by the rememberer. Falstaff is a figment who, having never existed, can never have been seen. Yet the idea of Falstaff may be quite as vivid as the idea of Lafayette. What, then, is the difference between the two states of mind? One, says J. S. Mill, is a belief about 'real facts'; the other about 'thoughts.' This, he observes, corresponds to James Mill's distinction between a 'sensation' and an 'idea,'[545] a difference which he had admitted to be 'primordial.' Then, says J. S. Mill, we may as well admit that there is an 'element' in the remembrance of a real fact not implied in the remembrance of a thought and not dependent on any difference in the 'ideas' themselves. It, too, may be taken as 'primordial,' or incapable of further analysis. This doctrine becomes important in some of Mill's logical speculations,[546] and is connected with his whole theory of belief in an external world. It has an uncomfortable likeness to Reid's 'common-sense' view, and even to the hated 'intuitionism'; and Mill deserves the more credit for his candour.
Meanwhile it seems clear that the criticism implies an important confusion. The line of distinction is drawn in the wrong place. So far as the simple 'imagination' is concerned, there may be no question of belief or disbelief. The picture of Falstaff or of Lafayette, a horse or a centaur, arises equally, and is put together, let us suppose, by simple association. But as soon as I think about either I believe or disbelieve, and equally whether I judge the object to be a thought or to be a 'real fact,' whether I say that I could have seen Lafayette, or that I could not have seen Falstaff. It is not a question between reality or unreality, but between two classes of reality. A dream is a real dream, just as a man is a real man. The question is simply where or how it exists, not whether it exists. The picture is, in one case, put together by my mind; in the other, due to a stimulus from without; but it exists in both cases; and belief is equally present whether I put it in one class of reality or the other: as we form a judgment equally when we pronounce a man to be lying, and when we pronounce him to be speaking the truth. J. S. Mill seems to suppose that association can explain the imagination of a centaur or a Falstaff, but cannot explain the belief in a horse or Lafayette. The imagination or 'ideation,' he should have said, accounts in both cases for the mere contents of the thought; but in neither case can it by itself explain the judgment as to 'reality.' That is to say, James Mill may have described accurately a part of the process by which the mental picture is constructed, but has omitted to explain the action of the mind itself. Belief, we may agree, is a 'primordial' or ultimate faculty; but we must not interpret it as belief in a 'real fact' as distinguished from belief in 'a thought': that is a secondary and incidental distinction.
This confusion, as I have said, apparently prevents J. S. Mill from seeing how deeply his very frank admissions cut into the very structure of his father's system. He has, as I have said, remarked upon the singular absence of any reference to 'belief,' 'abstraction,' and so forth; but he scarcely observes how much is implied by the omission. His criticism should have gone further. James Mill has not only omitted a faculty which enables us to distinguish between 'thoughts' and 'things,' images of fancy and pictures of reality, but also the faculty which is equally present whenever we properly think instead of simply seeing images passively; and equally whether we refer an image to fact or fancy. His 'analysis of the mind' seems to get rid of the mind itself.