It is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to.

I'm not trying to be anyone's savior. I just try to think about the future and not be sad

You need to live in a dome initially, but over time you could terraform Mars to look like Earth and eventually walk around outside without anything on... So it's a fixer-upper of a planet.

I think it’s important to reason from first principles rather than by analogy. The normal way we conduct our lives is we reason by analogy. [With analogy] we are doing this because it’s like something else that was done, or it is like what other people are doing. [With first principles] you boil things down to the most fundamental truths…and then reason up from there.

I could go and buy one of the islands in theBahamas and turn it into my personal fiefdom, but I am much more interested in trying to build andcreate a new company.

My proceeds from the PayPal acquisition were $180 million. I put $100 million in SpaceX, $70m in Tesla, and $10m in Solar City. I had to borrow money for rent.

Constantly seek criticism. A well thought out critique of whatever you’re doing is as valuable as gold.

Any product that needs a manual to work is broken.

In terms of the Internet, it's like humanity acquiring a collective nervous system. Whereas previously we were more like a [?], like a collection of cells that communicated by diffusion. With the advent of the Internet, it was suddenly like we got a nervous system. It's a hugely impactful thing.