 Let's turn to the topic of world peace, the book Better Angels of Our Nature. It will be available afterwards. Let me ask you a general question. Let's say it were possible by spending ten thousand dollars and devoting a few months of your life to it that any person on earth could blow up a significant part of a major city. They could buy something, some kind of explosive. It would cost them ten thousand dollars. How long would it take before someone actually did this? Anywhere on earth? Anywhere on earth. Seven billion people on earth. Any one of them that can come up with the 10k and have a desire to do it, which is not most people of course, but how long would it take before this would happen? Oh, I have no idea. And by blow up, do you mean like the Tsarnaev brothers or do you mean like Hiroshima? Like Hiroshima. Someone on earth anywhere. Maybe not too long, but I don't know. I couldn't really prophecy that. But let me then work back from that and ask you about your optimism, the debt piece. Is it then your belief it will never be that cheap to blow things up? You know, I don't know. My optimism doesn't consist of prophecy in that sense. That is my optimism consists of looking at what has happened and noting that first of all that the pessimistic view is factually incorrect, namely people believe that we're living in unusually violent times and we're not. What, how to project that into the future is a separate set of questions and there are many unknowns that I just I'm not arrogant enough to know the answer to. It's something that we could debate. We could explore them, but but I am not an optimist in the sense of saying, well, let's just extrapolate the curves in the future without asking questions like that. Maybe you could at least try to talk me out of my pessimism. Okay. What I see is that through the course of history as societies become wealthier, they also find destructive power is cheaper. Now for most people, even today, the destructive power at their hands, while it can be quite terrible, it's not enough to take out a major city or start a war. But the price of destructive power has been falling for as long as we've had economic growth. And it's hard for me to think of exceptions to that trend. So if I expect economic growth to continue, I expect we'll get in a world in some way a bit like my $10,000 question, how long would it take? And I worry that will happen a few times. And then we will cycle into some fairly significant form of disorder. And that's my default prediction. I don't quite mean to prophesize it. But I take that to be what one normally would expect. And I'm happy for you to talk me out of that. But what's the weakest premise in the chain I've given you? Well, I guess there are two, two. One is that every form of physical accomplishment follows an exponential curve of getting cheaper and cheaper. For example, plane travel hasn't gotten faster and faster. If you extrapolate from the Wright brothers to, say, 1957, then it is totally leveled off. In fact, if anything, it might be a little bit slower for a number of reasons. So it is not necessarily true that there'll be a $10,000 nuclear weapon. I'm not an expert on nuclear proliferation, but my reading is that there isn't. You still need the thousands of centrifuges and so on. So that's one, at least, topic to explore. Again, I'm not an optimist in saying, oh, relax, it'll never happen. But on the other hand, I think it's very easy. I think it's too easy to be a pessimist and to say that I can imagine bad things. Therefore, they are certain, which I think has been a default in a lot of our discourse. The other is, how much of a desire is there for that kind of destruction? I think the rate limiting step on terrorist destruction is how many people think that it's a good idea to cause a lot of damage for no particular reason. There could be Tsarnaev brothers in this audience, and there could be a pressure cooker that would blow up in the next few minutes. I don't think there will be, but clearly there's no technological or economic impediment to that. The amount of violence that we see is not limited by cost of technology. It's limited by the number of people who think that it would be a good idea to blow a lot of stuff up for no reason other than attracting publicity. And there are certain kinds of violence that are so pointless that just no one really wants to do it. One of the reasons that we've gone now more than 70 years without a nuclear weapon being used in war is that they're just not terribly useful as weapons to accomplish anything. I mean, they're useful to deter an existential threat and all-out invasion. That's presumably why North Korea wants them. But they haven't been used on the battlefield because leaving a huge radioactive crater is just not a very coherent war goal. You could imagine some apocalyptic cult where destruction for its own sake is so desirable that they would do anything possible. And we don't know how many people like that there are. Let me try. We don't know how many people like that there are, and I don't know the answer.