I think we ought always to entertain our opinions with some measure of doubt. I shouldn't wish people dogmatically to believe any philosophy, not even mine.

He will see himself and life and the world as truly as our human limitations will permit; realizing the brevity and minuteness of human life, he will realize also that in individual minds is concentrated whatever of value the known universe contains.

Although this may seem a paradox, all exact science is dominated by the idea of approximation. When a man tells you that he knows the exact truth about anything, you are safe in inferring that he is an inexact man. Every careful measurement in science is always given with the probable error ... every observer admits that he is likely wrong, and knows about how much wrong he is likely to be.

This idea of weapons of mass extermination is utterly horrible and is something which no one with one spark of humanity can tolerate.

The power of thought, the vast regions it can master.

If all our happiness is bound up entirely in our personal circumstances it is difficult not to demand of life more than it has to give.

Our individual life is brief, and perhaps the whole life of mankind will be brief if measured in astronomical scale