I came to the conclusion that we should aspire to increase the scope and scale of human consciousness in order to better understand what questions to ask. Really, the only thing that makes sense is to strive for greater collective enlightenment.

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.

When you struggle with a problem, that's when you understand it.

Every mode of transport that we use - whether it's planes, trains, automobiles, bikes, horses - is reusable, but not rockets. So we must solve this problem in order to become a space-faring civilization.

Facebook is quite entrenched and has a network effect. It's hard to break into a network once it's formed.

Some people don't like change, but you need to embrace change if the alternative is disaster.

I think that's the single best piece of advice: constantly think about how you could be doing things better and questioning yourself.