“Depression has its degrees which should be clearly marked. There is an absolute depression, when the very foundation of the psychic mechanism is damaged by pressures and we find it very difficult t...”

“I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettie...”

“To know the history of science is to recognize the mortality of any claim to universal truth. ”

“The scientist only imposes two things, namely truth and sincerity, imposes them upon himself and upon other scientists.”