The art of progress is to preserve order amid change and to preserve change amid order.

If a dog jumps in your lap, it is because he is fond of you; but if a cat does the same thing, it is because your lap is warmer.

The deepest definition of youth is life as yet untouched by tragedy.

There are no whole truths; all truths are half- truths. It is trying to treat them as whole truths that plays the devil.

Seek simplicity, and distrust it.

Periods of tranquility are seldom prolific of creative achievement. Mankind has to be stirred up.

Almost all really new ideas have a certain aspect of foolishness when they are first produced.

I have suffered a great deal from writers who have quoted this or that sentence of mine either out of its context or in juxtaposition to some incongruous matter which quite distorted my meaning , or destroyed it altogether.

The vitality of thought is in adventure. Ideas won't keep. Something must be done about them.

Civilization advances by extending the number of important operations which we can perform without thinking about them.

The only use of a knowledge of the past is to equip us for the present. The present contains all that there is. It is holy ground; for it is the past, and it is the future.

The future belongs to those who can rise above the confines of the earth.

Religion is what a person does in his solitariness.

I will not go so far as to say that to construct a history of thought without profound study of the mathematical ideas of successive epochs is like omitting Hamlet from the play which is named after him. . . But it is certainly analogous to cutting out the part of Ophelia. This simile is singularly exact. For Ophelia is quite essential to the play, she is very charming-- and a little mad.

Art is the imposing of a pattern on experience, and our aesthetic enjoyment is recognition of the pattern.

It requires a very unusual mind to undertake the analysis of the obvious.

If a dog jumps in your lap, it is because he is fond of you but if a cat does the same thing, it is because your lap is warmer.

But you can catch yourself entertaining habitually certain ideas and setting others aside; and that, I think, is where our personal destinies are largely decided.

Everything of importance has been said before by somebody who did not discover it.

Let us grant that the pursuit of mathematics is a divine madness of the human spirit, a refuge from the goading urgency of contingent happenings.

What is morality in any given time or place? It is what the majority then and there happen to like, and immorality is what they dislike.

There are no whole truths all truths are half- truths. It is trying to treat them as whole truths that plays the devil.

Ideas won't keep something must be done about them.

A clash of doctrines is not a disaster--it is an opportunity.

An enormous part of our mature experience cannot not be expressed in words.

Intelligence is quickness to apprehend as distinct from ability, which is capacity to act wisely on the thing apprehended.

It takes a very unusual mind to undertake the analysis of the obvious.

Nature gets credit which should in truth be reserved for ourselves: the rose for its scent, the nightingale for its song; and the sun for its radiance. The poets are entirely mistaken. They should address their lyrics to themselves and should turn them into odes of self congratulation on the excellence of the human mind.

Through and through the world is infested with quantity. To talk sense is to talk quantities, It is no use saying the nation is large- how large? It is no use s aying that radium is scarce- how scarce? You can not evade quantity. You may fly to poetry and music and quantity and number will face you in your rhythms and your octaves.

We think in generalities, but we live in detail.