The inquiry on which we are engaged belongs to the region of mind, and, therefore, after what has just been said, it will be apparent that I am entitled to adopt the standpoint of a spiritualist, to the extent of fastening attention only upon the mental side of the problem. For although the theory of Monism teaches, as against Spiritualism, that no one of the mental sequences could take place without a corresponding physical sequence, the theory also teaches the converse proposition; and therefore it makes no difference which of the two phenomenal sequences is taken as our index of the ontological. Now, it clearly makes a great difference whether the mental changes concerned in volition are regarded as effects or as causes. According to Materialism, the mental changes are the effects of cerebral changes, which were themselves the effects of precedent cerebral changes. According to Spiritualism, these mental changes are the causes, not only of the cerebral changes, but also of one another. According to Monism, the mental changes may be regarded as the causes of the cerebral, or _vice versa_, seeing that in neither case are we stating a real truth--the real truth being that it is only a cerebro-mental change which can cause any change either of cerebration or of mentation. Now it is evident that if the mental processes were always the effects of cerebral processes (Materialism), there could be no further question with regard to Liberty and Necessity; while, if the mental processes are the causes both of the cerebral processes and of one another (Spiritualism), the question before us becomes raised to a higher level. The causality in question being now regarded as purely mental, the will is no longer regarded as a passive slave of the brain, and the only thing to be considered is whether freedom is compatible with causation of a purely mental kind. Now, at an earlier stage of our enquiry I have argued that it is not; but this argument was based entirely upon spiritualistic premises, or upon the assumption that the principle of causality is everywhere external to, or independent of, the human mind--under which assumption I cannot see that it makes much difference whether the coercion comes from the brain alone, or from the whole general system of things external to the human mind. And here it is that I think the theory of Monism comes to the rescue.