Henri Poincaré was a French mathematician, theoretical physicist, engineer, and philosopher of science. He is often described as a polymath, and in mathematics as The Last Universalist by Eric Temple Bell, since he excelled in all fields of the discipline as it existed during his lifetime.
Description of Poincaré's Unconsciousness
Looking at One's Own Unconsciousness.
Before examining the latter conclusion, let us resume the history of that sleepless night which initiated all that memorable work, and which we set aside in the beginning because it offered very special characteristics.
"One evening," Poincare says, "contrary to my custom, I drank black coffee and could not sleep. Ideas rose in crowds; I felt them collide until pairs interlocked, so to speak, making a stable combination."
That strange phenomenon is perhaps the more interesting for the psychologist because it is more exceptional. Poincare lets us know that it is rather frequent as concerns himself: "It seems, in such cases, that one is present at his own unconscious work, made partially perceptible to the over-excited consciousness, yet without having changed its nature. Then we vaguely comprehend what distinguishes the two mechanisms or, if you wish, the working methods of the two egcs."
But that extraordinary fact of watching passively, as if from the outside, the evolution of subconscious ideas seems to be quite special to him. I have never experienced that marvelous sensation, nor have I ever heard of its happening to others.