The fish that first ventured ashore had considerable practical problems.

So much American science fiction is parochial - not as true now as it was years ago, but the assumption is one culture in the future, more or less like ours, and with the same ideals, the same notions of how to do things, just bigger and flashier technology. Well, you know darn well it doesn't work that way.

In my considered opinion, the profit to be made by permanent settlement in space is nothing less than the survival of industrial civilization, and therefore the survival of nearly the entire human race, along with such amenities as peace, freedom, enough to eat, and the chance to reach a high age in good health.

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

Colonization means potential immortality for the human genus. Man's safety on Earth was never great, and it dwindles hourly. Disarmament, even world government, will not guarantee survival in an age when population presses natural resources to the limit and when the knowledge of how to work mischief on a planetary scale is ever more widely diffused among peoples who may grow ever more desperate.

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

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.