The third law is, that a greater intensity of one of these impressions or of both is equivalent, in order to render them likely to excite each other, to a greater frequency of conjunction.1 Now or later, psychology ought to be able to explain the most complex phenomena by means of the laws of association. But its task is rendered very difficult, because the combined action of different causes sometimes produces combinations in which it is difficult to find the constituent elements. In fact, when a complex phenomenon is the result of several causes, two principal cases may present themselves: that of the mechanical, that of the chemical laws. In the case of the mechanical law, each cause is to be found in the effect, as if it had acted singly. The effect of concurrent causes is exactly the sum of the separate effects of each. On the contrary, the chemical combination of two substances produces a third whose proportions are completely different from each of the two others, whether taken separately or together. The laws of the phenomena of mind are analogous, now to mechanical, again to chemical laws. As an example of mental combination, we may give the colour white resulting from the rapid succession of the seven colours of the prism before our eyes. The idea of an orange, on the contrary, really results from the simple ideas of colour, form, taste, etc., because, when we interrogate our consciousness, we can discern all these sentiments in our idea. There are cases of mental chemistry in which it is more exact to say that simple ideas produce complex ideas, than to say that they compose them.2 The knowledge of the constituent elements of a complex fact in psychological chemistry, no more dispenses us from studying the fact itself, than the knowledge of the properties of oxygen and sulphur dispenses us from studying those of sulphuric acid. Mr. Mill (Logic, iii. 13; vi. 4) explains two great varieties of mind by two different modes of association. Simultaneous (or synchronical) associations predominate in persons endowed with keen organic sensibility; because it is an acknowledged fact that all the sensations or ideas experienced 1 Logic, book vi. ch. iv., and book iii. ch. vi. 2 Ibid. under a strong impression are intimately associated with each other. Now this predominance of synchronical associations produces a tendency to conceive of things under concrete forms, highly coloured, rich in attributes and details; a disposition of mind which is called imagination, and which is one of the faculties of the painter and of the poet. Successive associations predominate in less impressionable people. If they possess lofty intelligence, they will apply themselves to history or the sciences rather than to an art. The result of their inferior sensibility will be love of science, or of abstract truth, and lack of taste and warmth. Let us now consider associative psychology in antagonism with the notion of cause. IV. If the theory of consciousness and of exterior perception is the basis of all psychology, the theory of cause is the key of all philosophy; it even opens up to us regions into which we are not bound to penetrate. Let us keep to psychology. Thus Mr. Mill declares that he does not concern himself with the first or metaphysical cause of anything whatever.1 'The causes with which I concern myself are not efficient but physical causes. They are causes in that sense alone, in which one physical fact is said to be the cause of another. Of the efficient causes of phenomena, or whether any such causes exist at all, I am not called upon to give an opinion. The notion of causation is deemed, by the schools of metaphysics most in vogue at the present moment, to imply a mysterious and most powerful tie such as cannot, or at least does not exist, between any physical fact and that other physical fact on which it is invariably consequent, and which is popularly termed its cause; and thence is deduced the supposed necessity of ascending higher into the essences and inherent constitution of things to find the true cause, the cause which is not only followed by, but actually produces, the effect.2 1 Logic, book iii. ch. v. 2 Ibid. vol. i. p. 359, 4th edition. But Mr. Mill, as we may suppose, denies himself this excursion. In his Examination of Hamilton's Philosophy,1 he has sharply criticised that philosopher's theory of causality. According to Hamilton, the idea of cause is not a principle sui generis of our intelligence: it is explained by the impossibility of our conceiving of anything as absolutely commencing. It comes back to the axiom Ex nihilo nihil, in nihilum nil posse reverti. It is because we cannot conceive of nothing becoming something that we are always asking the cause of every effect, that is to say, that from which the effect draws its existence, and is only a transformation. If we examine Hamilton's doctrine, we shall see that, pushed to its ultimate consequences, it would end in giving to all phenomena an eternal substratum whose causes and effects would be only manifestations in time; that is to say, that it is completely opposed in spirit and tendencies to empiricism, whereas Mr. Mill acknowledges nothing but empirical causes. The phenomena of nature, he says, hold two different relations with respect to each other, simultaneousness and succession.2 Causality belongs to the category of relations of succession; but every relation of succession is not a relation of causality; in order to be so, it must fulfil essential conditions which we are about to determine. Certain facts succeed and, as we believe, always will succeed certain other facts. The invariable antecedent is called cause, the invariable consequent is called effect. The relation of cause to effect is ordinarily placed between a group of antecedents and a group of consequences, although, in general, by a quite arbitrary process, one of these antecedents is set apart under the name of cause, the others being called simply conditions. Thus a man eats of a certain aliment, and dies of it; it is said that this aliment is the cause of his death. But the true relation of causality is between the totality of the antecedents (the special constitu 1 An Examination, etc., ch. xvi. p. 340. tion of body, state of health, state of the atmosphere, etc.,) and the totality of the consequences (phenomena which constitute death). In the exact language proper to philosophy the cause is 'the sum of the positive and negative conditions taken together, the total of the contingencies of every nature which the consequence invariably follows, when they are realized.' This definition of cause is, however, only partial. Invariable sequence is not the synonym of causality; the sequence must also be unconditional. There are sequences as uniform as possible, which are not considered for that reason as cases of causality: thus, night invariably succeeds day, but probably no one has ever believed that the night is the cause of the day. This succession is not unconditional; the production of the day is subject to a condition which is not the anteriority of the night, but the presence of the sun. This is what authors wish to express when they say that the notion of cause implies the idea of necessity. Necessity signifies unconditionality. The cause of a phenomenon may therefore be defined as the antecedent, or the collection of antecedents, of which the phenomenon is invariably and unconditionally the consequent. But, to say that a case of succession is necessary, unconditional, in other words, invariable in every possible change of circumstances, is not this to acknowledge in causation an element of belief not derived from experience? By no means; it is experience itself which teaches us that such a succession is conditional, and that such another is not; that the succession of day and night, for example, is a derived succession, dependent on something else; in a word, experience, without anything to go beyond it, explains our ideas of causality.1 As for the theory which perceives in our voluntary activity the sole source of this idea, and which even maintains that it is that voluntary activity which reveals to us what is an efficient cause, Mr. Mill replies that he sees in the will only a physical cause like any other; that it is the cause of our corporeal actions, in the same manner as cold is the cause of ice, and a spark is the cause 1 Logic, book iii. ch. v. of the explosion of powder. Volition is the antecedent, the motion of our limbs is the consequent; but we have not direct consciousness of this sequence in the sense which the theory requires. Mr Mill, agreeing with Hamilton, bids us observe that it is refuted by the consideration, that between the overt fact of corporeal movement of which we are cognisant, and the internal act of mental determination, of which we are also cognisant, there intervenes a numerous series of intermediate agencies of which we have no knowledge; and, consequently, that we have no consciousness of any causal connexion between the extreme links of this chain, the volition to move, and the limb moving, as this hypothesis asserts.' 2 V. Thus then this fundamental idea of causality, implied in the most ordinary actions as in the loftiest knowledge, the basis of all science, the 'hidden root' of all induction; that is to say, according to our author, of all reasoning, is explained by experience pure and simple; it is only invariable and unconditional succession. Mr. Mill even refers axioms and necessary truths to experience. Let us observe, in the first place, that there are two sorts of general propositions, those which, according to everybody's belief, are born of experience and do not go beyond it, being no more than experience generalized (Example: All men are mortal); and those which, although suggested by experience, seem to go beyond it by their character of necessity (Example: Two parallels are everywhere equidistant). According to Mr. Mill, these latter propositions are neither truths à priori, as the rationalists would have them, nor are they mere words, as the nominalists with Hobbes at their head would have them. What are they then? Empirical propositions. This is how he establishes it. The reasons brought forward for granting a particular origin 1 Mill's Logic, book iii. chap. v. 2 Ibid. book iii. vol. i. p. 389, 5th edition. |