A moment's insight is sometimes worth a life's experience.

A person is always startled when he hears himself seriously called an old man for the first time.

I firmly believe that if the whole material medica, as now used, could be sunk to the bottom of the sea, it would be better for mankind-and all the worse for the fishes.

The truth is that the whole system of beliefs which comes in with the story of the fall of man ... is gently falling out of enlightened human intelligence.

Truth is tough. It will not break, like a bubble, at a touch; nay, you may kick it about all day like a football, and it will be round and full at evening.

A man may fulfill the object of his existence by asking a question he cannot answer, and attempting a task he cannot achieve.

Have the courage to act instead of react.