haps the existence of other active processes prevents its attaining that degree of intensity. Again, if we revert to the old soul theory, now almost wholly abandoned by psychologists, but still, I think, worthy of consideration, we may suppose that the cortical process alone can not produce consciousness, but requires the co-operation of some other factor. The pros and cons in these last two suppositions are too intricate for present discussion, and, indeed, my purpose is, not to prove a theory, but to state the fourth supposition and to analyze some of its logical implications.
The parallel theory would raise the presumption that any cortical process is accompanied by mental phenomena of some kind. We would then assume, in the case under consideration, that the cortical process in the auditory center generated a sound. But how is this to be reconciled to the testimony of consciousness that I heard no sound?
Well, it may be that I did hear it, but instantly forgot it, so that my present memory of that period contains no trace of it. That this frequently happens there can be no doubt, but there are many curious phenomena which require a further assumption, and that further assumption may be thus stated: The sound may have existed simply as a solitary sound, all alone, not in my consciousness or in the consciousness of any one, but as a bare mental event, related to my consciousness much as a sound in your consciousness is related to mine. It is not an easy conception to grasp, for our mental life always consists of many elements, and it would seem that this multiplicity is essentially involved in our notion of consciousness. Yet occasionally we have experiences which help us in forming the conception of a mental state existing outside a personal consciousness. I remember a trifling operation upon the eye which I once underwent. For a few seconds my consciousness seemed reduced to one element—a flood of frightful pain, which was not in my eye but seemed to pervade my whole being, to the almost complete exclusion of all else. Again, under nitrous oxide, my consciousness seemed reduced to something so rudimentary as to be wholly indescribable. I have heard of many similar experiences.
Without pronouncing upon the relative merits of the last two hypotheses I shall develop some of the logical implications of the latter. A state such as I have described, supposed to exist within my head, so to speak, but outside my consciousness, may be described as subconscious. There are, then, two conceivable ways in which a mental state may vanish from the upper consciousness. The cortical process upon which it depends may die away; it then perishes absolutely; or the cortical process may be dissociated from the system underlying the total consciousness and yet re-
