Look deep into nature, and then you will understand everything better.

Without the sense of fellowship with men of like mind, of preoccupation with the objective, the eternally unattainable in the field of art and scientific research, life would have seemed to me empty.

Given the millions of billions of Earth-like planets, life elsewhere in the Universe without a doubt, does exist. In the vastness of the Universe we are not alone.

When I think of the most able students I have encountered in my teaching - I mean those who have distinguished themselves not only by skill but by independence of thought - then I must confess that all have had a lively interest in epistemology.

As long as there are sovereign nations possessing great power, war is inevitable.

If I were to remain silent, I'd be guilty of complicity.

Violence sometimes may have cleared away obstructions quickly, but it never has proved itself creative.