When something is important enough, you do it even if the odds are not in your favor.

Going from PayPal, I thought: 'Well, what are some of the other problems that are likely to most affect the future of humanity?' Not from the perspective, 'What's the best way to make money?'

If you're trying to create a company, it's like baking a cake. You have to have all the ingredients in the right proportion.

There are really two things that have to occur in order for a new technology to be affordable to the mass market. One is you need economies of scale. The other is you need to iterate on the design. You need to go through a few versions.

The lessons of history would suggest that civilisations move in cycles. You can track that back quite far - the Babylonians, the Sumerians, followed by the Egyptians, the Romans, China. We're obviously in a very upward cycle right now and hopefully that remains the case. But it may not.

We have this handy fusion reactor in the sky called the sun, you don't have to do anything, it just works. It shows up every day.

Physics is a good framework for thinking. ... Boil things down to their fundamental truths and reason up from there.