To know the brain...is equivalent to ascertaining the material course of thought and will, to discovering the intimate history of life in its perpetual duel with external forces.

As long as our brain is a mystery, the universe, the reflection of the structure of the brain will also be a mystery.

In summary, all great work is the fruit of patience and perseverance, combined with tenacious concentration on a subject over a period of months or years.

The worst part is not in making a mistake but in trying to justify it, instead of using it as a heaven-sent warning of our mindlessness or our ignorance.

Every man if he so desires becomes sculptor of his own brain.

In the study of this membrane [the retina] I for the first time felt my faith in Darwinism (hypothesis of natural selection) weakened, being amazed and confounded by the supreme constructive ingenuity revealed not only in the retina and in the dioptric apparatus of the vertebrates but even in the meanest insect eye. ... I felt more profoundly than in any other subject of study the shuddering sensation of the unfathomable mystery of life.

Physical pain is easily forgotten, but a moral chagrin lasts indefinitely.