To this conception, which explains crystal-visions as a _form of the activity of the subconsciousness_, it will be variously objected, that such a simultaneous coexistence of two divisions of consciousness does not possess the same degree of probability as an alternation of states of consciousness. But how, upon this latter supposition, could the "Hibbs House" case be explained? In this instance, two psychical groups do not alternate, but one operates during the existence of the other. Further, the propriety in general is questioned of speaking of half-conscious or unconscious ideas and mental processes. It is the opinion of the Göttingen philosopher G. E. Müller, that just as every excitation of the brain immediately occasioned by a sensory stimulus is not competent to produce a sensation, so also all reproduced nervous excitations are not necessarily accompanied by perceptual images. In the cases mentioned, and in many others, there is no reason why groups of true _psychical_ states should be admitted, which, in contradistinction to other psychical states, only lack consciousness; on the contrary, we have to deal with simply a series of nervous excitations, which, as distinguished from other excitations, are not accompanied by corresponding states of our consciousness. This conception of soul-life, which has been of late very favorably received, Hugo Münsterberg has formulated thus—that the psychical phenomenon is to a certain extent the subjective internal aspect of a thus and thus constituted objective physical phenomenon. We are to bear in mind that the succession of the physical processes is nowhere interrupted, and that in addition certain of these physical processes, those namely which are carried on with a certain intensity in particular apparatuses of the brain, possess a psychical internal aspect; so that this excitation of the nervous cells is, without losing thereby anything in physical effect, the condition of the appearance of certain sensations in consciousness.