It may be well to remember that the highest level of moral aspiration recorded in history was reached by a few ancient Jews--Micah, Isaiah, and the rest--who took no count whatever of what might not happen to them after death. It is not obvious to me why the same point should not by and by be reached by the Gentiles.

The only people, scientific or other, who never make mistakes are those who do nothing.

Every great advance in natural knowledge has involved the absolute rejection of authority.

Life is like walking along a crowded street--there always seem to be fewer obstacles to getting along on the opposite pavement--and yet, if one crosses over, matters are rarely mended.

The question of all questions for humanity, the problem which lies behind all others and is more interesting than any of them, is that of the determination of man's place in nature and his relation to the cosmos.

Skepticism is the highest duty and blind faith the one unpardonable sin.

'Infidel' is a term of reproach, which Christians and Mohammedans, in their modesty, agree to apply to those who differ from them.