When one dreams that he is dreaming, which occasionally occurs, he is approaching the waking state; but since he cannot at that time sit in judgment fully on what he dreams without waking, it is equally clear that his state resembles that of a delirious person who may perceive that he is delirious and acknowledge it, but in a few seconds be again absorbed in what he sees.
Some of the most interesting achievements of the mind in dreams are the composition of poetry and the working out of mathematical problems. Dr. Abercrombie says that his friend Dr. Gregory told him that thoughts and even expressions which had occurred to him in dreams seemed to him so good when he awoke that he used them in his college lectures. Condorcet, having gone to bed before finishing certain profound calculations, said afterward that sometimes the conclusions of the work had been revealed to him in dreams. Dr. Abercrombie relates that Benjamin Franklin, than whose a more well-balanced and self-controlled mind never existed, assured Cabanis that the bearing and issue of political events which puzzled him when awake were not unfrequently unfolded to him in his dreams. Dr. Carpenter attempts to explain this by the theory well known as "unconscious cerebration." Like the terms of the phrenologists, this may describe but does not explain the process; and what it describes occurs frequently while we are awake. Not only in questions of memory, but in the profoundest thought, how often, when we have been compelled to turn from one class of work to another, and are, so far as our consciousness reports, entirely absorbed in it, in an instant a thought germane to the first problem which was occupying the mind appears with such clearness as to surpass in pertinency and value anything which we had previously
