Man can acquire accomplishments or he can become an animal, whichever he wants. God makes the animals, man makes himself.

As nations improve, so do their gods.

Man is a masterpiece of creation if for no other reason than that, all the weight of evidence for determinism notwithstanding, he believes he has free will.

I have often noticed that when people come to understand a mathematical proposition in some other way than that of the ordinary demonstration, they promptly say, "Oh, I see. That's how it must be." This is a sign that they explain it to themselves from within their own system.

With prophecies the commentator is often a more important man than the prophet.

People often become scholars for the same reason they become soldiers: simply because they are unfit for any other station. Their right hand has to earn them a livelihood; one might say they lie down like bears in winter and seek sustenance from their paws.

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.