Almost every way we make electricity today, except for the emerging renewables and nuclear, puts out CO2. And so, what we're going to have to do at a global scale, is create a new system. And so, we need energy miracles.

When I was in my 40s, Microsoft was my primary activity.

Our vision, which has not changed since the day the company was founded.

I really do think cancer will largely be a solved problem. I think most of the infectious diseases like malaria - our foundation is very involved - once we're finishing polio eradication, then starting up this malaria eradication, and getting that done as fast as we can.

The barrier to change is not too little caring; it is too much complexity. To turn caring into action, we need to see a problem, see a solution, and see the impact. But complexity blocks all three steps.

The ideal thing would be to have a 100 percent effective AIDS vaccine. And to have broad usage of that vaccine. That would literally break the epidemic.

Even for the very best programmers ah, sometimes you'll see someone else's program or somebody will come along and they'll show you what can be done in a simpler way.