A posteriori, however, definite facts are appealed to against freedom, some physical, others psychological. Sometimes it is asserted that our actions are necessitated by our feelings, our ideas, and the whole preceding series of our conscious states; sometimes freedom is denounced as being incompatible with the fundamental properties of matter, and in particular with the principle of the conservation of energy. Hence two kinds of determinism, two apparently different empirical proofs of universal necessity. We shall show that the second of these two forms is reducible to the first, and that all determinism, even physical determinism, involves a psychological hypothesis: we shall then prove that psychological determinism itself, and the refutations which are given of it, rest on an inaccurate conception of the multiplicity of conscious states, or rather of duration. Thus, in the light of the principles worked out in the foregoing chapter, we shall see a self emerge whose activity cannot be compared to that of any other force.
Physical determinism stated in the language of the molecular theory of matter.
Physical determinism, in its latest form, is closely bound up with mechanical or rather kinetic theories of matter. The universe is pictured as a heap of matter which the imagination resolves into molecules and atoms. These particles are supposed to carry out unceasingly movements of every kind, sometimes of vibration, sometimes of translation; and physical phenomena, chemical action, the qualities of matter which our senses perceive, heat, sound, electricity, perhaps even attraction, are thought to be reducible objectively to these elementary movements. The matter which goes to make up organized bodies being subject to the same laws, we find in the nervous system, for example, only molecules and atoms which are in motion and attract and repel one another. Now if all bodies, organized or unorganized, thus act and react on one another in their ultimate parts, it is obvious that the molecular state of the brain at a given moment will be modified by the shocks which the nervous system receives from the surrounding matter, so that the sensations, feelings and ideas which succeed one another in us can be defined as mechanical resultants, obtained by the compounding of shocks received from without with the previous movements of the atoms of the nervous substance. But the opposite phenomenon may occur; and the molecular movements which go on in the nervous system, if compounded with one another or with others, will often give as resultant a reaction of our organism on its environment: hence the reflex movements, hence also the so-called free and voluntary actions. As, moreover, the principle of the conservation of energy has been assumed to admit of no exception, there is not an atom, either in the nervous system or in the whole of the universe, whose position is not determined by the sum of the mechanical actions which the other atoms exert upon it. And the mathematician who knew the position of the molecules or atoms of a human organism at a given moment, as well as the position and motion of all the atoms in the universe capable of influencing it, could calculate with unfailing certainty the past, present and future actions of the person to whom this organism belongs, just as one predicts an astronomical phenomenon.[1]
If principle of conservation of energy is universal, physiological and nervous phenomena are necessitated, but perhaps not conscious states.
We shall not raise any difficulty about recognizing that this conception of physiological phenomena in general, and nervous phenomena in particular, is a very natural deduction from the law of the conservation of energy. Certainly, the atomic theory of matter is still at the hypothetical stage, and the purely kinetic explanations of physical facts lose more than they gain by being too closely bound up with it. We must observe, however, that, even if we leave aside the atomic theory as well as any other hypothesis as to the nature of the ultimate elements of matter, the necessitating of physiological facts by their antecedents follows from the theorem of the conservation of energy, as soon as we extend this theorem to all processes going on in all living bodies. For to admit the universality of this theorem is to assume, at bottom, that the material points of which the universe is composed are subject solely to forces of attraction and repulsion, arising from these points themselves and possessing intensities which depend only on their distances: hence the relative position of these material points at a given moment—whatever be their nature—would be strictly determined by relation to what it was at the preceding moment. Let us then assume for a moment that this last hypothesis is true: we propose to show, in the first place, that it does not involve the absolute determination of our conscious states by one another, and then that the very universality of the principle of the conservation of energy cannot be admitted except in virtue of some psychological hypothesis.
To prove conscious states determined, we should have to show a necessary connexion between them and cerebral states. No such proof.
Even if we assumed that the position, the direction and the velocity of each atom of cerebral matter are determined at every moment of time, it would not at all follow that our psychic life is subject to the same necessity. For we should first have to prove that a strictly determined psychic state corresponds to a definite cerebral state, and the proof of this is still to be given. As a rule we do not think of demanding it, because we know that a definite vibration of the tympanum, a definite stimulation of the auditory nerve, gives a definite note on the scale, and because the parallelism of the physical and psychical series has been proved in a fairly large number of cases. But then, nobody has ever contended that we were free, under given conditions, to hear any note or perceive any colour we liked. Sensations of this kind, like many other psychic states, are obviously bound up with certain determining conditions, and it is just for this reason that it has been possible to imagine or discover beneath them a system of movements which obey our abstract mechanics. In short, wherever we succeed in giving a mechanical explanation, we observe a fairly strict parallelism between the physiological and the psychological series, and we need not be surprised at it, since explanations of this kind will assuredly not be met with except where the two series exhibit parallel terms. But to extend this parallelism to the series themselves in their totality is to settle a priori the problem of freedom. Certainly this may be done, and some of the greatest thinkers have set the example; but then, as we said at first, it was not for reasons of a physical order that they asserted the strict correspondence between states of consciousness and modes of extension. Leibniz ascribed it to a preestablished harmony, and would never have admitted that a motion could give rise to a perception as a cause produces an effect. Spinoza said that the modes of thought and the modes of extension correspond with but never influence one another: they only express in two different languages the same eternal truth. But the theories of physical determinism which are rife at the present day are far from displaying the same clearness, the same geometrical rigour. They point to molecular movements taking place in the brain: consciousness is supposed to arise out of these at times in some mysterious way, or rather to follow their track like the phosphorescent line which results from the rubbing of a match. Or yet again we are to think of an invisible musician playing behind the scenes while the actor strikes a keyboard the notes of which yield no sound: consciousness must be supposed to come from an unknown region and to be superimposed on the molecular vibrations, just as the melody is on the rhythmical movements of the actor. But, whatever image we fall back upon, we do not prove and we never shall prove by any reasoning that the psychic fact is fatally determined by the molecular movement. For in a movement we may find the reason of another movement, but not the reason of a conscious state: only observation can prove that the latter accompanies the former. Now the unvarying conjunction of the two terms has not been verified by experience except in a very limited number of cases and with regard to facts which all confess to be almost independent of the will. But it is easy to understand why physical determinism extends this conjunction to all possible cases.
Physical determinism, when assumed to be universal, postulates psychological determinism.
Consciousness indeed informs us that the majority of our actions can be explained by motives. But it does not appear that determination here means necessity, since common sense believes in free will. The determinist, however, led astray by a conception of duration and causality which we shall criticise a little later, holds that the determination of conscious states by one another is absolute. This is the origin of associationist determinism, an hypothesis in support of which the testimony of consciousness is appealed to, but which cannot, in the beginning, lay claim to scientific rigour. It seems natural that this, so to speak, approximate determinism, this determinism of quality, should seek support from the same mechanism that underlies the phenomena of nature: the latter would thus convey to the former its own geometrical character, and the transaction would be to the advantage both of psychological determinism, which would emerge from it in a stricter form, and of physical mechanism, which would then spread over everything. A fortunate circumstance favours this alliance. The simplest psychic states do in fact occur as accessories to well-defined physical phenomena, and the greater number of sensations seem to be bound up with definite molecular movements. This mere beginning of an experimental proof is quite enough for the man who, for psychological reasons, is already convinced that our conscious states are the necessary outcome of the circumstances under which they happen. Henceforth he no longer hesitates to hold that the drama enacted in the theatre of consciousness is a literal and even slavish translation of some scenes performed by the molecules and atoms of organized matter. The physical determinism which is reached in this way is nothing but psychological determinism, seeking to verify itself and fix its own outlines by an appeal to the sciences of nature.
Is the principle of conservation of energy universal valid?