The difference between machines and human beings is that human beings can be reproduced by unskilled labour.

The limits of the possible can only be defined by going beyond them into the impossible.

I don't believe in astrology; I'm a Sagittarius and we're skeptical.

The only way to define your limits is by going beyond them.

The greatest tragedy in mankind's entire history may be the hijacking of morality by religion.

The moon is the first milestone on the road to the stars.

I'm sure the universe is full of intelligent life. It's just been too intelligent to come here.

Any sufficiently advanced technology is indistinguishable from magic.

There is hopeful symbolism in the fact that flags do not wave in a vacuum.

Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.

Until we get rid of religion, we won't be able to conduct the search for God.

To talk of a modern work of art enduring is sillier than talking of the eternal values of Standard Oil.

Science fiction is not about the freedom of imagination. It's about a free imagination pinched and howling in a vise that other people call real life.

To teach our kids what they need to know online, we have to talk to them off line.

Let us show that, if the people abandon the republicans, the republicans do not abandon the people.

The first lesson is that you can't lose a war if you have command of the air, and you can't win a war if you haven't.

Now I have enough money to travel wherever I want, but I haven't got the health.

What monstrosities would walk the streets were some people's faces as unfinished as their minds.

And verily for everything that a slave loses there is a substitute, but the one who loses Allah will never find anything to replace Him.

I don't do anything for Halloween. I carry Halloween inside of me.

You can find that sort of regularity in Stock Exchange quotations. [Expressing his lack of confidence in reported regularities in the periodic classification of elements.]