The great thing in the world is not so much to seek happiness as to earn peace and self-respect.

A world of facts lies outside and beyond the world of words.

In science, as in art, and, as I believe, in every other sphere of human activity, there may be wisdom in a multitude of counsellors, but it is only in one or two of them.

And when you cannot prove that people are wrong, but only that they are absurd, the best course is to let them alone.

Skepticism is the highest duty and blind faith the one unpardonable sin.

The mathematician starts with a few propositions, the proof of which is so obvious that they are called self-evident, and the rest of his work consists of subtle deductions from them. The teaching of languages, at any rate as ordinarily practiced, is of the same general nature authority and tradition furnish the data, and the mental operations are deductive.

When I reached intellectual maturity and began to ask myself whether I was an atheist, a theist, or a pantheist; a materialist, or an idealist; a Christian, or a freethinker; I found that the more I learned and reflected, the less ready was the answer; until, at last, I came to the conclusion that I had neither art nor part with any of these denominations, except the last.