In Harvest of Stars, there is this notion, not original with me of course, that it will become possible to download at least the basic aspects of a human personality into a machine program.

Anybody can find infinite Mandelbrot figures in his navel.

I have yet to see any problem, however complicated, which, when you looked at it in the right way, did not become still more complicated.

A fanatic's willingness to kill or be killed in the service of a cause cannot prove the rightness of that cause.

A fanatic is a man who, when he's lost sight of his purpose, redoubles his effort.

He had seen too much of the cosmos to have any great faith in man's ability to understand it.

If we knew exactly what to expect throughout the Solar System, we would have no reason to explore it.