Rarest of all is the man who can and does reason at all times, quickly, accurately, inclusively, despite hope or fear or bodily distress, without egocentric bias or thalmic disturbance, with correct memory, with clear distinction between fact, assumption, and non-fact.

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.

When it don’t rain, the roof don’t leak; when it rains, I can’t fix it nohow.

Of all the strange 'crimes' that human beings have legislated out of nothing, 'blasphemy' is the most amazing -- with 'obscenity' and 'indecent exposure' fighting it out for second and third place.

Faith strikes me as intellectual laziness.

It's an indulgence to sit in a room and discuss your beliefs as if they were a juicy piece of gossip.

Talking with a Martian is like talking with an echo. You don't get argument but you don't get results.