... the most essential characteristic of mind is memory, using this word in its broadest sense to include every influence of past experience on present reactions...

Aristotle maintained that women have fewer teeth than men; although he was twice married, it never occurred to him to verify this statement by examining his wives' mouths.

At the age of eleven, I began Euclid, with my brother as my tutor.... I had not imagined that there was anything so delicious in the world. After I had learned the fifth proposition, my brother told me that it was generally considered difficult, but I had found no difficulty whatsoever. This was the first time it had dawned on me that I might have some intelligence.

Broadly speaking, we are in the middle of a race between human skill as a means and human folly as an end.

But it is just this characteristic of simplicity in the laws of nature hitherto discovered which it would be fallacious to generalize, for it is obvious that simplicity has been a part cause of their discovery, and can, therefore, give no ground for the supposition that other undiscovered laws are equally simple

In attempting to understand the elements out of which mental phenomena are compounded, it is of the greatest importance to remember that from the protozoa to man there is nowhere a very wide gap either in structure or in behaviour. From this fact it is a highly probable inference that there is also nowhere a very wide mental gap..

John Locke invented common sense, and only Englishmen have had it ever since!

Mathematics is a subject in which we do not know what we are talking about, nor care whether what we say is true.

Mathematics possesses not only truth, but some supreme beauty - a beauty cold and austere, like that of sculpture.

One of the symptoms of approaching nervous breakdown is the belief that one's work is terribly important.

People are born ignorant, not stupid; they are made stupid by education.

The examination system, and the fact that instruction is treated mainly as a training for a livelihood, leads the young to regard knowledge from a purely utilitarian point of view as the road to money, not as the gateway to wisdom.

The trouble with the world is that the stupid are cocksure and the intelligent full of doubt.

The universe may have a purpose, but nothing we know suggests that, if so, this purpose has any similarity to ours.

There are infinite possibilities of error, and more cranks take up fashionable untruths than unfashionable truths.

Three passions, simple but overwhelmingly strong, have governed my life: the longing for love, the search for knowledge, and unbearable pity for the suffering of mankind.

To be able to fill leisure intelligently is the last product of civilization.

William James used to preach the 'will to believe.' For my part, I should wish to preach the 'will to doubt' ... what is wanted is not the will to believe, but the wish to find out, which is the exact opposite.

Work is of two kinds: first, altering the position of matter at or near the earth's surface relative to other such matter; second, telling other people to do so. The first kind is unpleasant and ill paid; the second is pleasant and highly paid.