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.