If there are any gods whose chief concern is man, they can't be very important gods.

The numbers of distinct human societies or nations, when our race is twice its present age, may be far greater than the total number of all the men who have ever lived up to the present time.

Humor was the enemy of desire.

It may be that the old astrologers had the truth exactly reversed, when they believed that the stars controlled the destinies of men. The time may come when men control the destinies of stars.

Anything that is theoretically possible will be achieved in practice, no matter what the technical difficulties are, if it is desired greatly enough.

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

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