Though Mill clings to reproduction and association with all his might, he is in spite of himself compelled to confess their impotence to solve some of the most vital questions of genetic psychology. He is constrained to introduce a new principle of fundamental importance, which is, in a way, the contrary of that of association. In the products of associations, the producing factors persist in the result as its components. In the process of "generation" which Mill assumes the generating factors effect their own disappearance in giving birth to their product. Its life is their death. Yet Mill is by no means clearly aware that he is deserting the association doctrine. He is rather of opinion that he is modifying and improving it. This is shown by his use of the term "Mental Chemistry." A chemical compound really is a compound. It really "consists" of its components and is not merely "generated" by them. Its weight is equal to their weight. By appropriate means the chemical combination can be dissolved so that the components again exist in a separate form. It is true that the compound has properties which do not belong to the components taken separately. But the components do not cease to exist in order to make way for the new properties as the generating factors in mental chemistry cease to exist in producing a new product. It may be said that though they do not cease to exist, they disappear just as the psychological factors disappear. But this is equivocation. The disappearance of the psychological factors is equivalent to their nonexistence: the disappearance of chemical factors merely means that there are certain ways in which they cease to manifest their presence to us. The analogy between the chemical process and the mental, as the mental is conceived by Mill, appears more plausible from another point of view. In order that oxygen and hydrogen may combine to form water they must first be brought together. Similarly, according to Mill, the generating factors of a new mental product must first be brought together in a firmly associated group or cluster before they annul each other and give place to something radically new. For this reason, he appears to have imagined that he was still following the lines of the association theory. But in so thinking he evidently fell into a "fallacy of confusion." What he affirms is that a preliminary process of association and reproduction precedes the generation of a new and simple mode of consciousness. What he tacitly assumes is that the process of generation itself is somehow reducible to association and reproduction. But this is mere confusion of thought. "Generation" remains an altogether distinct process from that which prepares the way for it. The fallacy had already been pointed out before Mill wrote in Thomas Brown's criticism of Condillac. "The great error of Condillac, as it appears to me, consists in supposing that when he has shown the circumstance from which any effect results he has shown this result to be essentially the same with the circumstance which produced it. Certain sensations have ceased to exist, certain other feelings have immediately arisen; these new feelings are, therefore, the others under another shape. Such is the secret, but very false logic, which seems to prevade his whole doctrine."* This applies mutatis mutandis to Mill. He held that because a certain grouping of mental elements precedes the emergence of a product distinct from each and all of them, this product must be the very elements themselves which have "melted and coalesced into one another." The metaphor of "melting and coalescence," if it is taken as more than a literary flourish, is quite unmeaning. Things which "melt and coalesce into one another" remain in existence after their union. The hydrogen and oxygen which unite to form water, persist, according to the principle of the indestructibility of matter, in the compound. It is only because of their persistence that they can properly be said to be compounded or to have coalesced. But there is no principle corresponding to the indestructibility of matter applying to modes of consciousness. They do not persist in their product, and therefore they do not "melt and coalesce" in it.

* Philosophy of the, Human Mind, Lecture xxxiii.

We have provisionally assumed Mill's theory that the "generation" of a new mode of consciousness by psychological conditions must be preceded by an associative grouping of the generating factors. But, in reality, this assumption is neither selfevident nor justified by experience. Mill, at this point, merely shows the strength of the bias which led him to affirm the Association theory, even in the act of denying it. From another point of view also, his account of "mental chemistry" is in the main, fictitious. He holds that the cooperative condition entirely disappears in giving rise to something new. This may happen in certain cases: but it is certainly not the prevailing rule, and above all it does not apply to the special class of cases which he refers to. Spatial perception, tactual and visual, in its various forms and modifications, is undoubtedly due to a vast complexity of cooperative conditions which do not appear in the result. But it is untrue that none of the contributory factors are discernible. Magnitude, as perceived by the eye, is colour extended or spread out. Shape, as perceived by the eye, is constituted by the boundaries of colour. In such perception there is always present at least visual sensation, and generally experiences accompanying eyemovements. The spatial character which belongs to these visual and motor experiences is indeed derivative and not a datum of primary sensation. It belongs to them, at least in the case of human beings, only in virtue of their previous combination in specific ways with other specific experiences, tactile, motor, and visual. None the less, the ocular perception of extended form and magnitude does not float loose in detachment from all the factors which contributed to its origin. For among these factors an essential part is played by the visual and motor sensations, which become endowed with a spatial character as the result of the process. What happens is not that a, b, c, d, e, the antecedent conditions, all disappear beyond recognition and leave behind them an x quite disparate from all or any of them. What happens is rather that one of these conditions has, through interaction with the others, acquired a peculiar modification, so that whenever it recurs, it recurs in a profoundly modified form.

What is true in the doctrine of mental chemistry is the denial, express or implied, that reproduction by association is the only principle of fundamental importance controlling the course of mental development.