6th. Solipsism.—The contention of this theory is that nothing exists save states of consciousness in the individual. Neither the material world nor other minds exist, save in the mind of the individual. This doctrine is so opposed to common sense and daily experience that it is unnecessary to dwell upon it.
7th. Inter-Actionism (Animism).—Here we have the world-old notion of soul and body existing as separate entities, influencing each other. Mind is here supposed to influence matter, and utilize it for the purposes of its manifestation.
That there are many facts difficult to account for on this theory cannot be doubted. Heredity and the origin of life must be taken into account; the "inconceivability" of the process has some weight; and the apparent infringement of the law of Conservation of Energy is a serious objection. Further, it may be urged, what evidence have we that consciousness can exist apart from brain-functioning? And, it may be said, apart from the facts offered by "psychical research," so-called, there is no evidence, strictly speaking. Hence the importance of these phenomena, if true. But the greatest objection to the doctrine of inter-actionism is doubtless that drawn from the law of the Conservation of Energy, which says that, inasmuch as mind is a non-physical energy, inasmuch as matter cannot be affected by a non-physical cause, brain-changes cannot result from will, or the activities of the mind.
But once prove that the human will is a physical energy, and this objection is readily disposed of. A physical energy is doubtless quite capable of causing all the changes within the brain which we know to exist within it—molecular, chemical, whatever they may be. It at once removes this classical objection to the doctrine of inter-actionism; and at the same time virtually proves that theory correct—thus solving this problem once and for all!
It may be pointed out, en passant, that philosophers and metaphysicians have really attacked this problem from the wrong standpoint—in their arguments concerning the relations of mind and brain—for this is a question which might have been (and in my opinion should have been) determined not by argument, but by fact. Instead of arguing, a priori, as to the nature of the connection, the problem might have been solved in the same way that all other problems are solved, viz., by an appeal to evidence and fact. The fundamental point made by practically all philosophers, in discussing this question, is that brain-states and conscious states are always found together, and that consciousness can never exist in the absence of brain. In other words, mind cannot exist as an "independent variable" in the world; it must always accompany a human brain.
I pass over, without comment, the fact that, according to the doctrines of idealistic monism and psycho-physical parallelism, this independence is virtually allowed, by the very nature of the doctrine; and shall point out merely that, if consciousness could be proved to exist independent of brain functioning, philosophic theories would have to be remodelled to conform to the evidence; the a priori problem could be settled at once by an appeal to actual fact. And again this separate existence of consciousness seems to be established by the facts of "psychical research," which apparently show that mind can exist apart from brain structure. This important fact once established, it would at once alter the whole case and render inter-actionism not only a "respectable" theory, but a proved fact.
So much for the importance of this doctrine (that the will is a physical energy) from the point of view of philosophy, and as applied to the question of the inter-relation of brain and mind. Now let us see if it cannot be applied in another direction.
The present interpretation of the character and nature of the will, and its inclusion as a physical energy, has a distinctly important bearing upon one of the most bitterly disputed points in the whole history of philosophy, viz., the question of the Freedom of the Will.
As is well known, there are two opposing views upon this subject—held by opposite schools—the theory of Determinism, on the one hand, and of Free Will on the other. The Libertarians assert that our wills are free—we having power of choice in all our actions. The Determinists, on the other hand, contend that our thoughts and actions are determined by definite, ascertainable causes. They contend that the feeling of freedom we all experience is but illusory, and that, in reality, our every action is inevitable—predetermined by its previous cause of causes, and could have been predicted by an intelligence wide enough and possessing a grasp deep enough of human nature to perceive life in all its tendencies. Indeed, one eminent philosopher went so far as to say that a belief in Free Will showed simple ignorance of science and a clinging to superstition!
A great deal has been written upon this subject of Free Will in the past; the point has been bitterly disputed for years. It may be said, however, that, at the present day, practically all philosophers and scientists, with few exceptions (e.g., James, Schiller, Bergson, etc.), believe in Determinism. The arguments for that doctrine are certainly weighty, and may be summarized, briefly, as follows: