That the psychical is not derivable from the physical, that it does not arise out of it, is not secondary to it, but pre-eminent over it, is not passive but creative; so much we have already gained to set over against naturalism. But its claims are even more affected by the fact of real psychical causality. We need not here concern ourselves with the difficult question, whether the mind can of itself act upon the body, and through it upon the external world. But in the logical consistence of naturalism there was implied not only a negative answer to this last question, but also a denial of the causality of the psychical, even within itself and its own domain. This is well illustrated in the figure of the cloud shadows. In consciousness state follows upon state, a upon b, b upon c. According to naturalism, b is not really the result of a, nor c of b, for in that case there would be independence of phenomena, and distinctness of laws in the psychical. But as all the states, a, b, and c, of the cloud shadows, depend upon states _a_, _b_, and _c_, of the clouds themselves, but do not themselves form a concatenation of causes, so all the states of the mind depend upon those of the body, in which alone there is a true chain of causes because they alone have true reality.
This is a complete distortion of the facts of the case. It would never be possible to persuade oneself or any one else that the arm, for instance, did not bend simply because we willed that it should. And it is still less possible to doubt that there are sequences of causes within the psychical, that in the world of thought and feeling, of desire and will, one thing calls up another, awakes it, impels it onwards, and influences it. Indeed, the mode of influence is peculiarly rich, subtle, and certain. Mental images and experiences arouse joy or sorrow, admiration or repulsion. One image calls up another, forces it to appear according to quite peculiar laws, or may crowd it out. Feelings call up desires, desires lead to determination. Good news actually causes joy, this is actually strengthened to willing, and the new situation gives rise to actual resolves. All this is so obvious and so unquestionable that no naturalism can possibly prevail against it. It has also long been made the subject of special investigation and carefully regulated experiment, and it is one of the chief subjects of modern psychological science. And especially as regards the different forms of “association of ideas,” the particular laws of this psychical causality have been established.