In proceeding to consider the opposite theories of Spiritualism and Materialism, it is before all else desirable to be perfectly clear upon the point of theory whereby they are essentially distinguished. This point is that which is raised by the question whether mind is the cause or the effect of motion. Both theories are dualistic, and therefore agree in holding that there is causation as between mind and motion: they differ only in their teaching as to the direction in which the causation proceeds. Of course, out of this fundamental difference there arise many secondary differences. The most important of these secondary differences has reference to the nature of the eternal or self-existing substance. Both theories agree that there is such a substance; but on the question whether this substance be mental or material, the two theories give contradictory answers, and logically so. For, if mind as we directly know it (namely, in ourselves) is taken to be a cause of motion, within our experience mind is accredited with priority; and hence the inference that elsewhere, or universally, mind is prior to motion. Furthermore, as motion cannot take place without something which moves, this something is likewise supposed to have been the result of mind: hence the doctrine of the creation by mind both of matter and of energy. On the other hand, the theory of materialism, by refusing to assign priority to mind as known directly in ourselves, naturally concludes that mind is elsewhere, or universally, the result of matter in motion--in other words, that matter in motion is the eternal or self-existing substance, and, as such, the cause of mind wherever mind occurs.