It's obviously tricky to convert cellulose to a useful biofuel. I think actually the most efficient way to use cellulose is to burn it in a co-generation power plant. That will yield the most energy and that is something you can do today.

If you had to buy a new plane every time you flew somewhere, it would be incredibly expensive.

With artificial intelligence, we are summoning the demon. In all those stories where there's the guy with the pentagram and the holy water, it's like, yeah, he's sure he can control the demon. Didn't work out.

The tough thing is figuring out what questions to ask, but […] once you do that, the rest is really easy.

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?'

We need to be super careful with AI. Potentially more dangerous than nukes.

Fear is a hard thing to deal with. I feel it quite strongly. If I think something is important enough, I'll make myself do it in spite of fear. But it can really sap the will. I hate fear, I wish I had it less.