We are concerned in public affairs, but immersed in our private ones.

Because the results are expressed in numbers, it is easy to make the mistake of thinking that the intelligence test is a measure like a foot ruler or a pair of scales. It is, of course, a quite different sort of measure. Intelligence is not an abstraction like length and weight; it is an exceedingly complicated notion - which nobody has yet succeeded in defining.

A man cannot sleep in his cradle: whatever is useful must in the nature of life become useless.

The tendency of the casual mind is to pick out or stumble upon a sample which supports or defies its prejudices, and then to make it the representative of a whole class.

Men can know more than their ancestors did if they start with a knowledge of what their ancestors had already learned....That is why a society can be progressive only if it conserves its traditions.

The only feeling that anyone can have about an event he does not experience is the feeling aroused by his mental image of that event ... For it is clear enough that under certain conditions men respond as powerfully to fictions as they do to realities.

There is but one bond of peace that is both permanent and enriching: The increasing knowledge of the world in which experiment occurs.