Can human choices be fully explained by physical causes?

In fact, if what thinks in my brain is not a part of this organ and therefore of the whole body, why does my blood boil, and the fever of my mind pass into my veins, when lying quietly in bed, I am forming the plan of some work or carrying on an abstract calculation? … In short, if the nerve-tension which causes pain occasions also the fever by which the distracted mind loses its will-power, and if, conversely, the mind too much excited, disturbs the body (and kindles that inner fire which killed Bayle while he was still so young) ; if an agitation rouses my desire and my ardent wish for what, a moment ago, I cared nothing about, and if in their turn certain brain impressions excite the same longing and the same desires, then why should we regard as double what is manifestly one being? In vain you fall back on the power of the will, since for one order that the will gives, it bows a hundred times to the yoke.^^

Man, then, is not a free agent in any one instant of his life; he is necessarily guided in each step by those advantages, whether real or fictitious, that he attaches to the objects by which his passions are roused: these passions themselves are necessary in a being who, unceasingly tends towards his own happiness; their energy is necessary, since that depends on his temperament; his temperament is necessary, because it depends on the physical elements which enter into his composition; the modification of this temperament is necessary, as it is the infallible result, the inevitable consequence of the impulse he receives from the incessant action of moral and physical beings.

They forget also that spirit can only exist on a substratum of organized matter, and that not the shadow of a proof can be brought forward to show that spirit can attain to an independent existence outside of matter. … Lastly they overlook that which in fact is proved everywhere, that if spirit and matter were opposites they could not act upon each other, nor in any essential respect be transmutable. The simple solution of the problem lies in the fact that not only physical but also psychical energies inhere in matter, and that the latter always become manifest wherever the necessary conditions are found, or that, wherever matter is arranged in a certain manner and moved in a certain way in the brain or the nervous system, the phenomena of sensation and thought are produced in similar fashion, as those of attraction and repulsion are under other conditions. *' If matter can fall to the ground then it can also think." — Schopenhauer. In the form of a stone it falls to the ground ; in the form of a muscle it con- tracts ; in the form of living nerve-substance it becomes capable of feeling and of thinking, or rises into self- consciousness.

The great struggle between the determinist and the indeterminist, between the opponent and the sustainer of the freedom of the will, has ended to-day, after more than two thousand years, completely in favor of the determinist. The human will has no more freedom than that of the higher animals, from which it differs only in degree, not in kind. In the last century the dogma of liberty was fought with general philosophic and cosmological arguments. The nineteenth century has given us very different weapons for its definitive destruction--the powerful weapons which we find in the arsenal of comparative physiology and evolution. We now know that each act of the will is as fatally determined by the organization of the individual and as dependent on the momentary condition of his environment as every other psychic activity. The character of the inclination was determined long ago by _heredity_ from parents and ancestors; the determination to each particular act is an instance of _adaptation_ to the circumstances of the moment wherein the strongest motive prevails, according to the laws which govern the statics of emotion.

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.

There can be no fully deterministic control of inorganic phenomena unless the determinism governs mind itself. Conversely if we wish to emancipate mind we must to some extent emancipate the material world also. There appears to be no longer any obstacle to this emancipation. Let us look more closely into the problem of how the mind gets a grip on material atoms so that movements of the body and limbs can be controlled by its volition. I think we may now feel quite satisfied that the volition is genuine. The materialist view was that the motions which appear to be caused by our volition are really reflex actions controlled by the material processes in the brain, the act of will being an inessential side phenomenon occurring simultaneously with the physical phenomena. But this assumes that the result of applying physical laws to the brain is fully determinate. It is meaningless to say that the behaviour of a conscious brain is precisely the same as that of a mechanical brain if the behaviour of a mechanical brain is left undetermined. If the laws of physics are not strictly causal the most that can be said is that the behaviour of the conscious brain is one of the possible behaviours of a mechanical brain. Precisely so; and the decision between the possible behaviours is what we call volition.