Why does the universe exist? Why is there — Okay. Okay. (Laughter) This is a cosmic mystery. Be solemn. Why is there a world, why are we in it, and why is there something rather than nothing at all? I mean, this is the super ultimate "why" question?

So I'm going to talk about the mystery of existence, the puzzle of existence, where we are now in addressing it, and why you should care, and I hope you do care. The philosopher Arthur Schopenhauer said that those who don't wonder about the contingency of their existence, of the contingency of the world's existence, are mentally deficient. That's a little harsh, but still. (Laughter) So this has been called the most sublime and awesome mystery, the deepest and most far-reaching question man can pose. It's obsessed great thinkers. Ludwig Wittgenstein, perhaps the greatest philosopher of the 20th century, was astonished that there should be a world at all. He wrote in his "Tractatus," Proposition 4.66, "It is not how things are in the world that is the mystical, it's that the world exists." And if you don't like taking your epigrams from a philosopher, try a scientist. John Archibald Wheeler, one of the great physicists of the 20th century, the teacher of Richard Feynman, the coiner of the term "black hole," he said, "I want to know how come the quantum, how come the universe, how come existence?" And my friend Martin Amis — sorry that I'll be doing a lot of name-dropping in this talk, so get used to it — my dear friend Martin Amis once said that we're about five Einsteins away from answering the mystery of where the universe came from. And I've no doubt there are five Einsteins in the audience tonight. Any Einsteins? Show of hands? No? No? No? No Einsteins? Okay.

So this question, why is there something rather than nothing, this sublime question, was posed rather late in intellectual history. It was towards the end of the 17th century, the philosopher Leibniz who asked it, a very smart guy, Leibniz, who invented the calculus independently of Isaac Newton, at about the same time, but for Leibniz, who asked why is there something rather than nothing, this was not a great mystery. He either was or pretended to be an Orthodox Christian in his metaphysical outlook, and he said it's obvious why the world exists: because God created it. And God created, indeed, out of nothing at all. That's how powerful God is. He doesn't need any preexisting materials to fashion a world out of. He can make it out of sheer nothingness, creation ex nihilo. And by the way, this is what most Americans today believe. There is no mystery of existence for them. God made it.

So let's put this in an equation. I don't have any slides so I'm going to mime my visuals, so use your imaginations. So it's God + nothing = the world. Okay? Now that's the equation. And so maybe you don't believe in God. Maybe you're a scientific atheist or an unscientific atheist, and you don't believe in God, and you're not happy with it. By the way, even if we have this equation, God + nothing = the world, there's already a problem: Why does God exist? God doesn't exist by logic alone unless you believe the ontological argument, and I hope you don't, because it's not a good argument. So it's conceivable, if God were to exist, he might wonder, I'm eternal, I'm all-powerful, but where did I come from? (Laughter) Whence then am I? God speaks in a more formal English. (Laughter) And so one theory is that God was so bored with pondering the puzzle of His own existence that He created the world just to distract himself. But anyway, let's forget about God. Take God out of the equation: We have ________ + nothing = the world. Now, if you're a Buddhist, you might want to stop right there, because essentially what you've got is nothing = the world, and by symmetry of identity, that means the world = nothing. Okay? And to a Buddhist, the world is just a whole lot of nothing. It's just a big cosmic vacuity. And we think there's a lot of something out there but that's because we're enslaved by our desires. If we let our desires melt away, we'll see the world for what it truly is, a vacuity, nothingness, and we'll slip into this happy state of nirvana which has been defined as having just enough life to enjoy being dead. (Laughter)

So that's the Buddhist thinking. But I'm a Westerner, and I'm still concerned with the puzzle of existence, so I've got ________ + — this is going to get serious in a minute, so — ________ + nothing = the world. What are we going to put in that blank? Well, how about science? Science is our best guide to the nature of reality, and the most fundamental science is physics. That tells us what naked reality really is, that reveals what I call TAUFOTU, the True And Ultimate Furniture Of The Universe. So maybe physics can fill this blank, and indeed, since about the late 1960s or around 1970, physicists have purported to give a purely scientific explanation of how a universe like ours could have popped into existence out of sheer nothingness, a quantum fluctuation out of the void. Stephen Hawking is one of these physicists, more recently Alex Vilenkin, and the whole thing has been popularized by another very fine physicist and friend of mine, Lawrence Krauss, who wrote a book called "A Universe from Nothing," and Lawrence thinks that he's given — he's a militant atheist, by the way, so he's gotten God out of the picture. The laws of quantum field theory, the state-of-the-art physics, can show how out of sheer nothingness, no space, no time, no matter, nothing, a little nugget of false vacuum can fluctuate into existence, and then, by the miracle of inflation, blow up into this huge and variegated cosmos we see around us.

Okay, this is a really ingenious scenario. It's very speculative. It's fascinating. But I've got a big problem with it, and the problem is this: It's a pseudo-religious point of view. Now, Lawrence thinks he's an atheist, but he's still in thrall to a religious worldview. He sees physical laws as being like divine commands. The laws of quantum field theory for him are like fiat lux, "Let there be light." The laws have some sort of ontological power or clout that they can form the abyss, that it's pregnant with being. They can call a world into existence out of nothing. But that's a very primitive view of what a physical law is, right? We know that physical laws are actually generalized descriptions of patterns and regularities in the world. They don't exist outside the world. They don't have any ontic cloud of their own. They can't call a world into existence out of nothingness. That's a very primitive view of what a scientific law is. And if you don't believe me on this, listen to Stephen Hawking, who himself put forward a model of the cosmos that was self-contained, didn't require any outside cause, any creator, and after proposing this, Hawking admitted that he was still puzzled. He said, this model is just equations. What breathes fire into the equations and creates a world for them to describe? He was puzzled by this, so equations themselves can't do the magic, can't resolve the puzzle of existence. And besides, even if the laws could do that, why this set of laws? Why quantum field theory that describes a universe with a certain number of forces and particles and so forth? Why not a completely different set of laws? There are many, many mathematically consistent sets of laws. Why not no laws at all? Why not sheer nothingness?

So this is a problem, believe it or not, that reflective physicists really think a lot about, and at this point they tend to go metaphysical, say, well, maybe the set of laws that describes our universe, it's just one set of laws and it describes one part of reality, but maybe every consistent set of laws describes another part of reality, and in fact all possible physical worlds really exist, they're all out there. We just see a little tiny part of reality that's described by the laws of quantum field theory, but there are many, many other worlds, parts of reality that are described by vastly different theories that are different from ours in ways we can't imagine, that are inconceivably exotic. Steven Weinberg, the father of the standard model of particle physics, has actually flirted with this idea himself, that all possible realities actually exist. Also, a younger physicist, Max Tegmark, who believes that all mathematical structures exist, and mathematical existence is the same thing as physical existence, so we have this vastly rich multiverse that encompasses every logical possibility.

Now, in taking this metaphysical way out, these physicists and also philosophers are actually reaching back to a very old idea that goes back to Plato. It's the principle of plenitude or fecundity, or the great chain of being, that reality is actually as full as possible. It's as far removed from nothingness as it could possibly be.

So we have these two extremes now. We have sheer nothingness on one side, and we have this vision of a reality that encompasses every conceivable world at the other extreme: the fullest possible reality, nothingness, the simplest possible reality. Now what's in between these two extremes? There are all kinds of intermediate realities that include some things and leave out others. So one of these intermediate realities is, say, the most mathematically elegant reality, that leaves out the inelegant bits, the ugly asymmetries and so forth. Now, there are some physicists who will tell you that we're actually living in the most elegant reality. I think that Brian Greene is in the audience, and he has written a book called "The Elegant Universe." He claims that the universe we live in mathematically is very elegant. Don't believe him. (Laughter) It's a pious hope, I wish it were true, but I think the other day he admitted to me it's really an ugly universe. It's stupidly constructed, it's got way too many arbitrary coupling constants and mass ratios and superfluous families of elementary particles, and what the hell is dark energy? It's a stick and bubble gum contraption. It's not an elegant universe. (Laughter) And then there's the best of all possible worlds in an ethical sense. You should get solemn now, because a world in which sentient beings don't suffer needlessly, in which there aren't things like childhood cancer or the Holocaust. This is an ethical conception. Anyway, so between nothingness and the fullest possible reality, various special realities. Nothingness is special. It's the simplest. Then there's the most elegant possible reality. That's special. The fullest possible reality, that's special.

But what are we leaving out here? There's also just the crummy, generic realities that aren't special in any way, that are sort of random. They're infinitely removed from nothingness, but they fall infinitely short of complete fullness. They're a mixture of chaos and order, of mathematical elegance and ugliness. So I would describe these realities as an infinite, mediocre, incomplete mess, a generic reality, a kind of cosmic junk shot. And these realities, is there a deity in any of these realities? Maybe, but the deity isn't perfect like the Judeo-Christian deity. The deity isn't all-good and all-powerful. It might be instead 100 percent malevolent but only 80 percent effective, which pretty much describes the world we see around us, I think. (Laughter) So I would like to propose that the resolution to the mystery of existence is that the reality we exist in is one of these generic realities. Reality has to turn out some way. It can either turn out to be nothing or everything or something in between. So if it has some special feature, like being really elegant or really full or really simple, like nothingness, that would require an explanation. But if it's just one of these random, generic realities, there's no further explanation for it. And indeed, I would say that's the reality we live in. That's what science is telling us. At the beginning of the week, we got the exciting information that the theory of inflation, which predicts a big, infinite, messy, arbitrary, pointless reality, it's like a big frothing champagne coming out of a bottle endlessly, a vast universe, mostly a wasteland with little pockets of charm and order and peace, this has been confirmed, this inflationary scenario, by the observations made by radio telescopes in Antarctica that looked at the signature of the gravitational waves from just before the Big Bang. I'm sure you all know about this. So anyway, I think there's some evidence that this really is the reality that we're stuck with.

Now, why should you care? Well — (Laughter) — the question, "Why does the world exist?" that's the cosmic question, it sort of rhymes with a more intimate question: Why do I exist? Why do you exist? you know, our existence would seem to be amazingly improbable, because there's an enormous number of genetically possible humans, if you can compute it by looking at the number of the genes and the number of alleles and so forth, and a back-of-the-envelope calculation will tell you there are about 10 to the 10,000th possible humans, genetically. That's between a googol and a googolplex. And the number of the actual humans that have existed is 100 billion, maybe 50 billion, an infinitesimal fraction, so all of us, we've won this amazing cosmic lottery. We're here. Okay.

So what kind of reality do we want to live in? Do we want to live in a special reality? What if we were living in the most elegant possible reality? Imagine the existential pressure on us to live up to that, to be elegant, not to pull down the tone of it. Or, what if we were living in the fullest possible reality? Well then our existence would be guaranteed, because every possible thing exists in that reality, but our choices would be meaningless. If I really struggle morally and agonize and I decide to do the right thing, what difference does it make, because there are an infinite number of versions of me also doing the right thing and an infinite number doing the wrong thing. So my choices are meaningless. So we don't want to live in that special reality. And as for the special reality of nothingness, we wouldn't be having this conversation. So I think living in a generic reality that's mediocre, there are nasty bits and nice bits and we could make the nice bits bigger and the nasty bits smaller and that gives us a kind of purpose in life. The universe is absurd, but we can still construct a purpose, and that's a pretty good one, and the overall mediocrity of reality kind of resonates nicely with the mediocrity we all feel in the core of our being. And I know you feel it. I know you're all special, but you're still kind of secretly mediocre, don't you think? (Laughter) (Applause)

So anyway, you may say, this puzzle, the mystery of existence, it's just silly mystery-mongering. You're not astonished at the existence of the universe and you're in good company. Bertrand Russell said, "I should say the universe is just there, and that's all." Just a brute fact. And my professor at Columbia, Sidney Morgenbesser, a great philosophical wag, when I said to him, "Professor Morgenbesser, why is there something rather than nothing?" And he said, "Oh, even if there was nothing, you still wouldn't be satisfied."

So — (Laughter) — okay. So you're not astonished. I don't care. But I will tell you something to conclude that I guarantee you will astonish you, because it's astonished all of the brilliant, wonderful people I've met at this TED conference, when I've told them, and it's this: Never in my life have I had a cell phone. Thank you. (Laughter) (Applause)