It is decreed by a merciful Nature that the human brain cannot think of two things simultaneously, so that if it be steeped in curiosity as to science it has no room for merely personal considerations.

To let the brain work without sufficient material is like racing an engine. It racks itself to pieces. The sea air, sunshine, and patience, Watson—all else will come.

consider that a man's brain originally is like a little empty attic, and you have to stock it with such furniture as you choose. A fool takes in all the lumber of every sort that he comes across, so that the knowledge which might be useful to him gets crowded out, or at best is jumbled up with a lot of other things, so that he has a difficulty in laying his hands upon it.

There comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones.

It is decreed by a merciful Nature that the human brain cannot think of two things simultaneously . . .

Crime is common. Logic is rare.

My mind rebels at stagnation. Give me problems, give me work, give me the most abstruse cryptogram, or the most intricate analysis, and I am in my own proper atmosphere. I can dispense with artificial stimulants. But I abhor the dull routine of existence. I crave for mental exaltation.

The girl made an impression on me, and I forgot her; the other made no impression, and her I can remember.

Let pessimism once take hold of the mind, and life is all topsy-turvy, all vanity and vexation of spirit. There is no cure for individual or social disorder, except in forgetfulness and annihilation.

Life is not entertainment. Life is not distraction.

I still believe that the university is a place where people can develop their minds and learn skills, but also they can develop their personalities and their spiritual life.

I think the first thing to do is to be aware that you can choose what you're thinking about and that your life is going down the path that you're thinking.