The Principle of Tolerance, fixed once for all the realization that all knowledge is limited. It is an irony of history that at the very time when this was being worked out, there should rise, under Hitler in Germany and other tyrants elsewhere, a counter-conception: a principle of monstrous certainty. When the future looks back on the 1930's, it will think of them as a crucial confrontation of culture as I have been expounding it - the ascent of man against the throwback to the despots' belief that they have absolute certainty.

We are all shot through with enough motives to make a massacre, any day of the week that we want to give them their head.

Science is a tribute to what we can know, although we are fallible.

Knowledge is not a loose leaf notebook of facts.

You will die but the carbon will not; its career does not end with you. It will return to the soil, and there a plant may take it up again in time, sending it once more on a cycle of plant and animal life.

Satire is not a social dynamite. But it is a social indicator: it shows that new men are knocking at the door.

The basis for poetry and scientific discovery is the ability to comprehend the unlike in the like and the like in the unlike.