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

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.

The single definition of government I've ever seen that makes sense is that it's the organization which claims the right to kill people who won't do what it wants.

Machines can only find what ignorant men have programmed them to find.

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

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.

What five books would I like to be remembered for? Well... Tau Zero, I like that one especially. It was somewhat of a tour de force, and I think it got across what I was trying for.