The lowest-hanging fruit in preventative medicine is just to really focus on nutrition.

The most contrarian thing of all is not to oppose the crowd but to think for yourself.

For a new payment product, you always have to ask, how much better is it than the current solution? So when we started Paypal, for eBay micro merchants, it was much better than getting the 7 to 10 days process of cashing a check in the mail. When you look at stores or physical worlds, places, a lot of these places are already set up to take cash or credit card. Apple Pay may be an incremental improvement, maybe a little bit better. But when you have something that's pretty good and you go to something that's perfect, sometimes it's very hard to drive adoption because the delta is not that big.

Consider the trivial but revealing hallmarks of urban hipsterdom: faux vintage photography, the handlebar mustache, and vinyl record players all hark back to an earlier time when people were still optimistic about the future. If everything worth doing has already been done, you may as well feign an allergy to achievement and become a barista.

One of the reasons I think people are increasingly nervous about U.S. debt is because they think that we are not actually digging ourselves out of the hole, but instead are digging ourselves into a deeper and deeper hole and will not be able to pay it back because we're not actually creating the new technologies that will enable us to pay back and the money somehow is not really being invested in the future or in progress.

We need more pessimism that the future might be a lot worse, and we need more optimism that the future might be better.

We might describe our world as having retail sanity, but wholesale madness.