If all mankind were suddenly to practice honesty, many thousands of people would be sure to starve.

The more experiences and experiments accumulate in the exploration of nature, the more precarious the theories become. But it is not always good to discard them immediately on this account. For every hypothesis which once was sound was useful for thinking of previous phenomena in the proper interrelations and for keeping them in context. We ought to set down contradictory experiences separately, until enough have accumulated to make building a new structure worthwhile.

The most perfect ape cannot draw an ape; only man can do that; but, likewise, only man regards the ability to do this as a sign of superiority.

A clever child brought up with a foolish one can itself become foolish. Man is so perfectible and corruptible he can become a fool through good sense.

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

Here take back the stuff that I am, nature, knead it back into the dough of being, make of me a bush, a cloud, whatever you will, even a man, only no longer make me.

Everyone should study at least enough philosophy and belles-lettres to make his sexual experience more delectable.