I have directed your attention up to this point to the conservation of experiences which at the time of their occurrence, although lost beyond voluntary recall, for the most part occupied the focus of attention of the individual—were within the full light of consciousness. If these experiences were the only ones which were subject to conservation—and I would have you still bear in mind that I am using the term only in the limited sense of the ability to recover an experience in some favorable condition, or moment of consciousness, or through some fortunate or technical mode of reproduction—if, I say, these were the only ones to be conserved, then the conservation of the experiences which make up our mental lives would be considerably curtailed. It so happens, however, that a large part of our mental activity is occupied with acts of which at the moment we are only dimly aware—or half aware—in that they do not occupy the focus of attention. Some of these are what we call absent-minded acts. Again, many sensations and perceptions do not enter the focus of attention, so that we are either not aware of them, or, if we are, there is so little vividness attached to them that they are almost immediately lost to voluntary memory. The same is true of certain trains of thoughts which course through the mind while one’s attention is concentrated on some other line of thought. They are sometimes described as being in the background of the mind. Then, again, we have our dream life, and that of reverie, and the important artificial state of hypnosis; also certain pathological states to which some individuals are subject, such as intoxication, hysterical crises, deliria, and multiple personality. Accordingly it is important in any investigation into the extent of the field of conservation to inquire whether all this mental life is only fleeting, evanescent, psychological experience, or whether it is subject to the same principle of conservation. If the latter be the case it presages consequences which are portentous in the possible multiplicity and manifoldness of the elements which may enter into and may govern the mechanism of mental processes. But let me not get ahead of my exposition.