Doubt must be no more than vigilance, otherwise it can become dangerous.

It is too bad if you have to do everything upon reflection and can't do anything from early habit.

Man is a masterpiece of creation . . .

One of our forefathers must have read a forbidden book.

If all else fails, the character of a man can be recognized by nothing so surely as by a jest which he takes badly.

What is called an acute knowledge of human nature is mostly nothing but the observer's own weaknesses reflected back from others.

There is no greater impediment to progress in the sciences than the desire to see it take place too quickly.