The rules of logic are to mathematics what those of structure are to architecture.

Never let yourself be diverted, either by what you wish to believe, or what you think could have beneficent social effects if it were believed; but look only and solely at what are the facts.

There seems scarcely any limit to what could be done in the way of producing a good world, if only men would use science wisely.

Is the set of all sets which are not members of themselves a member of itself?

The wise man will be as happy as circumstances permit, and if he finds the contemplation of the universe painful beyond a point, he will contemplate something else instead.

Cynicism such as one finds very frequently among the most highly educated young men and women of the West, results from the combination of comfort and powerlessness.

A man without a bias cannot write interesting history - if indeed such a man exists.