Causality, as the prefiguring of the future phenomenon in its present conditions, in one form destroys concrete phenomena.
In the first place, mathematics furnishes us with one type of this kind of prefiguring. The very movement by which we draw the circumference of a circle on a sheet of paper generates all the mathematical properties of this figure: in this sense an unlimited number of theorems can be said to pre-exist within the definition, although they will be spread out in duration for the mathematician who deduces them. It is true that we are here in the realm of pure quantity and that, as geometrical properties can be expressed in the form of equations, it is easy to understand how the original equation, expressing the fundamental property of the figure, is transformed into an unlimited number of new ones, all virtually contained in the first. On the contrary, physical phenomena, which succeed one another and are perceived by our senses, are distinguished by quality not less than by quantity, so that there would be some difficulty in at once declaring them equivalent to one another. But, just because they are perceived through our sense-organs, we seem justified in ascribing their qualitative differences to the impression which they make on us and in assuming, behind the heterogeneity of our sensations, a homogeneous physical universe. Thus, we shall strip matter of the concrete qualities with which our senses clothe it, colour, heat, resistance, even weight, and we shall finally find ourselves confronted with homogeneous extensity, space without body. The only step then remaining will be to describe figures in space, to make them move according to mathematically formulated laws, and to explain the apparent qualities of matter by the shape, position, and motion of these geometrical figures. Now, position is given by a system of fixed magnitudes and motion is expressed by a law, i.e. by a constant relation between variable magnitudes; but shape is a mental image, and, however tenuous, however transparent we assume it to be, it still constitutes, in so far as our imagination has, so to speak, the visual perception of it, a concrete and therefore irreducible quality of matter. It will therefore be necessary to make a clean sweep of this image itself and replace it by the abstract formula of the movement which gives rise to the figure. Picture then algebraical relations getting entangled in one another, becoming objective by this very entanglement, and producing, by the mere effect of their complexity, concrete, visible, and tangible reality,—you will be merely drawing the consequences of the principle of causality, understood in the sense of an actual prefiguring of the future in the present. The scientists of our time do not seem, indeed, to have carried abstraction so far, except perhaps Lord Kelvin. This acute and profound physicist assumed that space is filled with a homogeneous and incompressible fluid in which vortices move, thus producing the properties of matter: these vortices are the constituent elements of bodies; the atom thus becomes a movement, and physical phenomena are reduced to regular movements taking place within an incompressible fluid. But, if you will notice that this fluid is perfectly homogeneous, that between its parts there is neither an empty interval which separates them nor any difference whatever by which they can be distinguished, you will see that all movement taking place within this fluid is really equivalent to absolute immobility, since before, during, and after the movement nothing changes and nothing has changed in the whole. The movement which is here spoken of is thus not a movement which actually takes place, but only a movement which is pictured mentally: it is a relation between relations. It is implicitly supposed, though perhaps not actually realized, that motion has something to do with consciousness, that in space there are only simultaneities, and that the business of the physicist is to provide us with the means of calculating these relations of simultaneity for any moment of our duration. Nowhere has mechanism been carried further than in this system, since the very shape of the ultimate elements of matter is here reduced to a movement. But the Cartesian physics already anticipated this interpretation; for if matter is nothing, as Descartes claimed, but homogeneous extensity, the movements of the parts of this extensity can be conceived through the abstract law which governs them or through an algebraical equation between variable magnitudes, but cannot be represented under the concrete form of an image. And it would not be difficult to prove that the more the progress of mechanical explanations enables us to develop this conception of causality and therefore to relieve the atom of the weight of its sensible qualities, the more the concrete existence of the phenomena of nature tends to vanish into algebraical smoke.
It thus leads to Descartes' physics and Spinoza's metaphysics, but cannot bind future to present without neglecting duration.
Thus understood, the relation of causality is a necessary relation in the sense that it will indefinitely approach the relation of identity, as a curve approaches its asymptote. The Principle of identity is the absolute law of our consciousness: it asserts that what is thought is thought at the moment when we think it: and what gives this principle its absolute necessity is that it does not bind the future to the present, but only the present to the present: it expresses the unshakable confidence that consciousness feels in itself, so long as, faithful to its duty, it confines itself to declaring the apparent present state of the mind. But the principle of causality, in so far as it is supposed to bind the future to the present, could never take the form of a necessary principle; for the successive moments of real time are not bound up with one another, and no effort of logic will succeed in proving that what has been will be or will continue to be, that the same antecedents will always give rise to identical consequents. Descartes understood this so well that he attributed the regularity of the physical world and the continuation of the same effects to the constantly renewed grace of Providence; he built up, as it were, an instantaneous physics, intended for a universe the whole duration of which might as well be confined to the present moment. And Spinoza maintained that the indefinite series of phenomena, which takes for us the form of a succession in time, was equivalent, in the absolute, to the divine unity: he thus assumed, on the one hand, that the relation of apparent causality between phenomena melted away into a relation of identity in the absolute, and, on the other, that the indefinite duration of things was all contained in a single moment, which is eternity. In short, whether we study Cartesian physics, Spinozistic metaphysics, or the scientific theories of our own time, we shall find everywhere the same anxiety to establish a relation of logical necessity between cause and effect, and we shall see that this anxiety shows itself in a tendency to transform relations of succession into relations of inherence, to do away with active duration, and to substitute for apparent causality a fundamental identity.
The necessary determination of phenomena implies non-duration; but we endure and are therefore free.
Now, if the development of the notion of causality, understood in the sense of necessary connexion, leads to the Spinozistic or Cartesian conception of nature, inversely, all relation of necessary determination established between successive phenomena may be supposed to arise from our perceiving, in a confused form, some mathematical mechanism behind their heterogeneity. We do not claim that common sense has any intuition of the kinetic theories of matter, still less perhaps of a Spinozistic mechanism; but it will be seen that the more the effect seems necessarily bound up with the cause, the more we tend to put it in the cause itself, as a mathematical consequence in its principle, and thus to cancel the effect of duration. That under the influence of the same external conditions I do not behave to-day as I behaved yesterday is not at all surprising, because I change, because I endure. But things considered apart from our perception do not seem to endure; and the more thoroughly we examine this idea, the more absurd it seems to us to suppose that the same cause should not produce to-day the effect which it produced yesterday. We certainly feel, it is true, that although things do not endure as we do ourselves, nevertheless there must be some reason why phenomena are seen to succeed one another instead of being set out all at once. And this is why the notion of causality, although it gets indefinitely near that of identity, will never seem to us to coincide with it, unless we conceive clearly the idea of a mathematical mechanism or unless some subtle metaphysics removes our very legitimate scruples on the point. It is no less obvious that our belief in the necessary determination of phenomena by one another becomes stronger in proportion as we are more inclined to regard duration as a subjective form of our consciousness. In other words, the more we tend to set up the causal relation as a relation of necessary determination, the more we assert thereby that things do not endure like ourselves. This amounts to saying that the more we strengthen the principle of causality, the more we emphasize the difference between a physical series and a psychical one. Whence, finally, it would result (however paradoxical the opinion may seem) that the assumption of a relation of mathematical inherence between external phenomena ought to bring with it, as a natural or at least as a plausible consequence, the belief in human free will. But this last consequence will not concern us for the moment: we are merely trying here to trace out the first meaning of the word causality, and we think we have shown that the prefiguring of the future in the present is easily conceived under a mathematical form, thanks to a certain conception of duration which, without seeming to be so, is fairly familiar to common sense.
Prefiguring, as having an idea of a future act which we cannot realize without effort, does not involve necessary determination.
But there is a prefiguring of another kind, still more familiar to our mind, because immediate prefiguring, as consciousness gives us the type of it. We go, in fact, through successive states of consciousness, and although the later was not contained in the earlier, we had before us at the time a more or less confused idea of it. The actual realization of this idea, however, did not appear as certain but merely as possible. Yet, between the idea and the action, some hardly perceptible intermediate processes come in, the whole mass of which takes for us a form sui generis, which is called the feeling of effort. And from the idea to the effort, from the effort to the act, the progress has been so continuous that we cannot say where the idea and the effort end, and where the act begins. Hence we see that in a certain sense we may still say here that the future was prefigured in the present; but it must be added that this prefiguring is very imperfect, since the future action of which we have the present idea is conceived as realizable but not as realized, and since, even when we plan the effort necessary to accomplish it, we feel that there is still time to stop. If, then, we decide to picture the causal relation in this second form, we can assert a priori that there will no longer be a relation of necessary determination between the cause and the effect, for the effect will no longer be given in the cause. It will be there only in the state of pure possibility and as a vague idea which perhaps will not be followed by the corresponding action. But we shall not be surprised that this approximation is enough for common sense if we think of the readiness with which children and primitive people accept the idea of a whimsical Nature, in which caprice plays a part no less important than necessity. Nay, this way of conceiving causality will be more easily understood by the general run of people, since it does not demand any effort of abstraction and only implies a certain analogy between the outer and the inner world, between the succession of objective phenomena and that of our subjective states.
This second conception of causality leads to Leibniz as the first led to Spinoza.
In truth, this second way of conceiving the relation of cause to effect is more natural than the first in that it immediately satisfies the need of a mental image. If we look for the phenomenon Β within the phenomenon A, which regularly precedes it, the reason is that the habit of associating the two images ends in giving us the idea of the second phenomenon wrapped up, as it were, in that of the first. It is natural, then, that we should push this objectification to its furthest limit and that we should make the phenomenon A itself into a psychic state, in which the phenomenon Β is supposed to be contained as a very vague idea. We simply suppose, thereby, that the objective connexion of the two phenomena resembles the subjective association which suggested the idea of it to us. The qualities of things are thus set up as actual states, somewhat analogous to those of our own self; the material universe is credited with a vague personality which is diffused through space and which, although not exactly endowed with a conscious will, is led on from one state to another by an inner impulse, a kind of effort. Such was ancient hylozoism, a half-hearted and even contradictory hypothesis, which left matter its extensity although attributing to it real conscious states, and which spread the qualities of matter throughout extensity while treating these qualities as inner i.e. simple states. It was reserved for Leibniz to do away with this contradiction and to show that, if the succession of external qualities or phenomena is understood as the succession of our own ideas, these qualities must be regarded as simple states or perceptions, and the matter which supports them as an unextended monad, analogous to our soul. But, if such be the case, the successive states of matter cannot be perceived from the outside any more than our own psychic states; the hypothesis of pre-established harmony must be introduced in order to explain how these inner states are representative of one another. Thus, with our second conception of the relation of causality we reach Leibniz, as with the first we reached Spinoza. And in both cases we merely push to their extreme limit or formulate with greater precision two half-hearted and confused ideas of common sense.