The appearance of strength is all about you. It would seem to last forever. However... the rotten tree-trunk, until the very moment when the storm-blast breaks it in two, has all the appearance of might it ever had. The storm-blast whistles through the branches of the Empire even now. Listen... and you will hear the creaking.

The day you stop learning is the day you begin decaying.

Intelligence is a valuable thing, but it is not usually the key to survival. Sheer fecundity ... usually counts. The intelligent gorilla doesn't do as well as the less intelligent but more-fecund rat, which doesn't do as well as the still-less-intelligent but still-more-fecund cockroach, which doesn't do as well as the minimally-intelligent but maximally-fecund bacterium.

When asked for advice by beginners. Know your ending, I say, or the river of your story may finally sink into the desert sands and never reach the sea.

A good question is, of course, the key by which infinite answers can be educed.

Although we will hate and fight the machines, we will be supplanted anyway, and rightly so, for the intelligent machines to which we will give birth may, better than we, carry on the striving toward the goal of understanding and using the Universe, climbing to heights we ourselves could never aspire to.

When I feel difficulty coming on, I switch to another book I'm writing. When I get back to the problem, my unconscious has solved it.