Insofar as the facts are concerned, it would be well, I think, to establish two categories--(1) static unconscious, comprising habits, memory, and, in general, all that is organized knowledge. It is a state of preservation, of rest; very relatively, since representations suffer incessant corrosion and change. (2) Dynamic unconscious, which is a state of latent activity, of elaboration and incubation. We might give a multitude of proofs of this unconscious rumination. The well-known fact that an intellectual work gains by being interrupted; that in resuming it one often finds it cleared up, changed, even accomplished, was explained by some psychologists prior to Carpenter by "the resting of the mind." It would be just as valid to say that a traveler covers leagues by lying abed. The author just mentioned[159] has brought together many observations in which the solution of a mathematical, mechanical, commercial problem appeared suddenly after hours and days of vague, undefinable uneasiness, the cause of which is unknown, which, however, is only the result of an underlying cerebral working; for the trouble, sometimes rising to anguish, ceases as soon as the unawaited conclusion has entered consciousness. The men who think the most are not those who have the clearest and "most conscious" ideas, but those having at their disposal a rich fund of unconscious elaboration. On the other hand, shallow minds have a naturally poor unconscious fund, capable of but slight development; they give out immediately and rapidly all that they are able to give; they have no reserve. It is useless to allow them time for reflection or invention. They will not do better; they may do worse. As to the nature of the unconscious working, we find disagreement and darkness. One may doubtless maintain, theoretically, that in the inventor everything goes on in subconsciousness and in unconsciousness, just as in consciousness itself, with the exception that a message does not arrive as far as the self; that the labor that may be followed, in clear consciousness, in its progress and retreats, remains the same when it continues unknown to us. This is possible. Yet it must at least be recognized that consciousness is rigorously subject to the condition of time, the unconscious is not. This difference, not to mention others, is not negligible, and could well arouse other problems. The contemporary theories regarding the nature of the unconscious seem to me reducible to two principal positions--one psychological, the other physiological. 1. The physiological theory is simple and scarcely permits any variations. According to it, unconscious activity is simply cerebral; it is an "unconscious cerebration." The psychic factor, which ordinarily accompanies the activity of the nervous centers, is absent. Although I incline toward this hypothesis, I confess that it is full of difficulties.