When one has to ask, "Am I really in love?" the answer is always "No".

The dinosaurs disappeared because they could not adapt to their changing environment. We shall disappear if we cannot adapt to an environment that now contains spaceships, computers - and thermonuclear weapons.

Space can be mapped and crossed and occupied without definable limit; but it can never be conquered.

Now I understand,” said the last man.

Excessive interest in pathological behavior was itself pathological

Only small minds are impressed by large numbers.

I don't think there is such a thing as as a real prophet. You can never predict the future. We know why now, of course; chaos theory, which I got very interested in, shows you can never predict the future.