The question that will decide our destiny is not whether we shall expand into space. It is: shall we be one species or a million? A million species will not exhaust the ecological niches that are awaiting the arrival of intelligence.

Science was blamed for all the horrors of World War I, just as it's blamed today for nuclear weapons and quite rightly. I mean World War I was a horrible war and it was mostly the fault of science, so that was in a way a very bad time for science, but on the other hand we were winning all these Nobel Prizes.

The language that nature speaks is the same language that we invented for mathematics. That's just an amazing piece of luck, which we don't understand.

The whole point of science is that most of it is uncertain. That's why science is exciting--because we don't know. Science is all about things we don't understand. The public, of course, imagines science is just a set of facts. But it's not. Science is a process of exploring, which is always partial. We explore, and we find out things that we understand. We find out things we thought we understood were wrong. That's how it makes progress.

I think that the artificial-intelligence people are making a lot of noise recently, claiming that artificial intelligence is making huge progress and we're going to be outstripped by the machines.

Technology without morality is barbarous; morality without technology is impotent.

Younger people have so many opportunities. I don't see any pessimism among them.