When one door is closed, don't you know that many more are open

After all, science is essentially international, and it is only through lack of the historical sense that national qualities have been attributed to it.

Maybe you are searching among the branches, for what only appears in the roots.

I like to think of myself at home in the armchair, writing, smoking and occasionally wandering down the shop.

I will not let anyone walk through my mind with their dirty feet.

I am only one, but still I am one. I cannot do everything, but still I can do something; and because I cannot do everything, I will not refuse to do something that I can do.

Thought is free.

I have noticed that nothing I have never said ever did me any harm.

Words have no power to impress the mind without the exquisite horror of their reality.

There is no terror in the bang, only in the anticipation of it.

Comedy is acting out optimism.

To the young people I say, you are a gift to your communities and indeed the world. You are our hope and our future.

When the dog looks at you, the dog is not thinking what kind of a person you are. The dog is not judging you.

In terms of an identity, an identity reflects an individuality, by definition. And, if there is a quality present, it is recognizable and it can be named. If you can't name it, it means you don't recognize it.

It is a process of diverting one's scattered forces into one powerful channel.

A scientific man ought to have no wishes, no affections, - a mere heart of stone.

Common sense is the most widely shared commodity in the world, for every man is convinced that he is well supplied with it.

It is by no means an irrational fancy that, in a future existence, we shall look upon what we think our present existence, as a dream.

Be like a tree and let the dead leaves drop.

I don't say we all ought to misbehave, but we ought to look as if we could.

As we look ahead into the next century, leaders will be those who empower others.