Liberty is never unalienable, it must be redeemed regularly with the blood of patriots or it always vanishes.

There ought not to be anything in the whole universe that man can't poke his nose into-that's the way we're built and I assume that there's some reason for that.

Never try to have the last word. You might get it.

If you happen to be one of the fretful minority who can do creative work, never force an idea; you'll abort it if you do. Be patient and you'll give birth to it when the time is ripe. Learn to wait.

Pessimist by policy, optimist by temperament- it is possible to be both. How? By never taking an unnecessary chance and by minimizing the risks you can't avoid. This permits you to play out the game untroubled by the certainty of the outcome.

We came here for a small, informal meeting. We find you've turned it into a circus. Well, if you're going to have a circus, you've got to have elephants.

In this complex world, the scientific method, and the consequences of the scientific method are central to everything the human race is doing and to wherever we are going.