There is a difference between what technology enables and what historical business practices enable.

If you really could take the CO2, when you burn hydrocarbons - coal, for example - if you could really capture the carbon and sequester it - they call it CCS - if the extra capital cost, energy cost, and storage costs over time didn't make it super expensive, then that's another path that you could go down.

The trick generally is to break programs into pieces and have those pieces be individually testable and so then when you move on to the other pieces you treat it as a black box knowing that it either works or doesn't work.

Cutting through complexity to find a solution runs through four predictable stages: determine a goal, find the highest-leverage approach, discover the ideal technology for that approach, and in the meantime, make the smartest application of the technology that you already have - whether it's something sophisticated, like a drug, or something simpler, like a bednet.

I think of myself as a global citizen.

With polio, we've gone several years with no polio in all of Africa, but now with this we're having to go and mop up in that whole region, so it's a bit of a setback for polio. So in parallel we have to go back and get rid of those cases.

I never took a day off in my twenties. Not one.