[Theodore Roosevelt] was a naturalist on the broadest grounds, uniting much technical knowledge with knowledge of the daily lives and habits of all forms of wild life. He probably knew tenfold more natural history than all the presidents who had preceded him, and, I think one is safe in saying, more human history also.

One can only learn his powers of action by action, and his powers of thought by thinking

I have discovered the secret of happiness - it is work, either with the hands or the head. The moment I have something to do, the draughts are open and my chimney draws, and I am happy.

Basically [United States and France] said "We will use nuclear weapons whenever it suits our purposes to do so." So this expansion of doctrines regarding possible use of nuclear weapons makes them more, you know, sort of, salient and important and so it's increasing the perceived political value of nuclear weapons and therefore causing or contributing to possible proliferation.

If you think you can do it, you can.

The rocks are not so close akin to us as the soil; they are one more remove from us; but they lie back of all, and are the final source of all. ... Time, geologic time, looks out at us from the rocks as from no other objects in the landscape.

Blessed is the man who has some congenial work, some occupation in which he can put his heart, and which affords a complete outlet to all the forces there are in him.