It's Bill Gates's birthday. When I interviewed him, he showed me how his brain works so differently than anyone else I've ever met.

In person, he was much like you'd imagine from the endless reports on him: appreciably geeky, pleasantly courteous, and intensely intelligent.

When he spoke, Gates made broad gestures with his hands, seemingly sculpting clean-energy solutions with his hands while reeling off global development statistics, like how tiny China's philanthropic class is (under 0.1% of the overall economy), how huge the energy market is ($3 trillion a year), and how humanity went from 33% of children dying by age 5 to below 5%.

That was what was so spectacular about talking to the man, now freshly 64 years old. He has an encyclopedic knowledge of so many things, appropriate for a guy who plowed through the entirety of "World Book Encyclopedia" as a teen, and he holds in mind the way fields interact with one another. 

Let's consider, in its lengthy entirety, his response to my first question, "What are the most exciting things happening right now in clean energy?"

His reply: 

A lot of it is pretty early stage. The most straightforward path would be if we could bring the cost of solar electric and wind down by another factor of say, three, and then have some miraculous storage solution, so that not only over the 24-hour day but over long periods of time where the wind doesn't blow, you have reliable energy. That's a path. But energy storage is hard. That's not a guaranteed path.

In fact, batteries haven't improved over the last 100 years as much as they would need to in order to make that happen. So I'm invested in a lot of battery companies — and there's a lot that exists I'm not in. They're all having a tough time achieving it. We need to look at less obvious paths, things like the wind in the jet stream, which is very high up. The material science of what type of kite string you would need to connect up to that. That's still at the basic research level.

That's the part where the governments have a unique role, and then when it progresses well enough, then existing companies or new startup companies should take it. In the $3 trillion a year energy market, the rewards will be quite fantastic.

At some point, that risk-taking private capital can take over, and have patents and trade secrets and things that let them lead the way, which happened with the steam engine and some other things. Although with energy, the time of adoption is a lot longer than it is with, say, IT products or even medical advances, like drugs and vaccines.

Other paths would include making nuclear fission cheap enough and safe enough that people broadly embrace it, so that could be scaled up. Or, 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.

I could name about a dozen paths, and you'd like to have a whole bunch of research on all those paths, and then, eventually, at least four to five companies with really significant financing try and get to big scale, going down and really trying to prove it out.

Then, in the same way that when the car got going, people thought it would be an electric car; people thought it would be a steam car. Actually, the dark horse in that race was internal combustion, but because of the energy density of gasoline and discovery of oil in large amounts at that point, in first Pennsylvania and then Texas, it won out over those other two, to the point that those other two are actually viewed as obscure footnotes in history.

The first thing you notice is that those are ready-to-be published paragraphs coming out of his mouth; it's a Sunday op-ed coming off the top of his head. But consider the many threads interwoven in his comment, which reveal one of the unique forms of genius he has.

First, Gates runs through the state of energy storage, which has lots of potential but is very hard to pull off. (The national capacity has quadrupled over the past five years, however.) Then battery technology. Then the role of government in innovation, and with that, private capital. Then nuclear fission. Then carbon capture. Then how that new market would begin to mature.

And then, the bit I find especially charming, regarding the intellectual humility needed in a revolution, since you don't know how a revolution is going to pan out. People thought the electric car was going to be the killer app, and then the steam car, and gasoline was the actual dark horse. And that itself was powered by the discovery of oil in Pennsylvania and Texas. So, adding to the state of many arts in the technological race for clean energy, Gates delivered a bite-size lesson in how technological shifts actually happen and the nature of innovation. 

That brings us back to the encyclopedias that Gates gobbled up as a Seattle-area adolescent. The word "encyclopedia" has a rather poetic etymology, "enkuklios paideia," or all-around education. This is what Gates displays in conversation, a stunning understanding of how everything relates to everything else. 

Gates is the billionaire version of what the University of Texas psychologist Art Markman calls an "expert generalist." Someone who doesn't just know a little about a lot but a lot about a lot — like Picasso getting into African art and initiating cubism. Gates has studied energy and materials and public health and a thousand other things. He is such an evangelist of intersectional knowledge that he's pushed the discipline of "Big History," which seeks to tell "the story of the universe from the big bang to the first signs of life to today's complex societies," according to a 2018 Gates blog post. 

Thanks to Gates and his peers, we live in a world of information, as the cliché goes. You can ask Siri or Alexa for just about any particular fact, and they'll give it to you without you even needing to look at your phone. But what Gates has is more powerful than information — he possesses knowledge, a breadth of it. 

Research on learning suggests that the more you know, the easier it is to find and retain new knowledge, in a process called elaboration — you're tying the new thing to what you already know. So if you already have a ton of nodes to tie things to, it'll probably be easier to get new insights about material science, or whatever, to actually stick. It's compounding interest but for knowing stuff.  

"The more you learn," Gates said in another profile, "the more you have a framework that the knowledge fits into."

This post extensively expands on an earlier piece.