Don't ever become a pessimist... a pessimist is correct oftener than an optimist, but an optimist has more fun, and neither can stop the march of events.

If you've got the truth you can demonstrate it. Talking doesn't prove it.

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

Theology is never any help; it is searching in a dark cellar at midnight for a black cat that isn't there. Theologians can persuade themselves of anything.

The second best thing about space travel is that the distances involved make war very difficult, usually impractical, and almost always unnecessary. This is probably a loss for most people, since war is our race's most popular diversion, one which gives purpose and color to dull and stupid lives. But it is a great boon to the intelligent man who fights only when he must-never for sport.

With eternity to draw on there could be no reason for hurrying - 'hurry' was not a concept in Martian.

Never pick up a stray kitten . . . unless you've already made up your mind to be owned by it.