I have a question: Who here remembers when they first realized they were going to die?

　　I do. I was a young boy, and my grandfather had just died, and I remember a few days later lying in bed at night trying to make sense of what had happened. What did it mean that he was dead? Where had he gone? It was like a hole in reality had opened up and swallowed him. But then the really shocking question occurred to me: If he could die, could it happen to me too? Could that hole in reality open up and swallow me? Would it open up beneath my bed and swallow me as I slept? Well, at some point, all children become aware of death. It can happen in different ways, of course, and usually comes in stages. Our idea of death develops as we grow older. And if you reach back into the dark corners of your memory, you might remember something like what I felt when my grandfather died and when I realized it could happen to me too, that sense that behind all of this the void is waiting.

　　And this development in childhood reflects the development of our species. Just as there was a point in your development as a child when your sense of self and of time became sophisticated enough for you to realize you were mortal, so at some point in the evolution of our species, some early human's sense of self and of time became sophisticated enough for them to become the first human to realize, "I'm going to die." This is, if you like, our curse. It's the price we pay for being so damn clever. We have to live in the knowledge that the worst thing that can possibly happen one day surely will, the end of all our projects, our hopes, our dreams, of our individual world. We each live in the shadow of a personal apocalypse.

　　And that's frightening. It's terrifying. And so we look for a way out. And in my case, as I was about five years old, this meant asking my mum. Now when I first started asking what happens when we die, the grown-ups around me at the time answered with a typical English mix of awkwardness and half-hearted Christianity, and the phrase I heard most often was that granddad was now "up there looking down on us," and if I should die too, which wouldn't happen of course, then I too would go up there, which made death sound a lot like an existential elevator. Now this didn't sound very plausible. I used to watch a children's news program at the time, and this was the era of space exploration. There were always rockets going up into the sky, up into space, going up there. But none of the astronauts when they came back ever mentioned having met my granddad or any other dead people. But I was scared, and the idea of taking the existential elevator to see my granddad sounded a lot better than being swallowed by the void while I slept. And so I believed it anyway, even though it didn't make much sense.

　　And this thought process that I went through as a child, and have been through many times since, including as a grown-up, is a product of what psychologists call a bias. Now a bias is a way in which we systematically get things wrong, ways in which we miscalculate, misjudge, distort reality, or see what we want to see, and the bias I'm talking about works like this: Confront someone with the fact that they are going to die and they will believe just about any story that tells them it isn't true and they can, instead, live forever, even if it means taking the existential elevator. Now we can see this as the biggest bias of all. It has been demonstrated in over 400 empirical studies. Now these studies are ingenious, but they're simple. They work like this. You take two groups of people who are similar in all relevant respects, and you remind one group that they're going to die but not the other, then you compare their behavior. So you're observing how it biases behavior when people become aware of their mortality. And every time, you get the same result: People who are made aware of their mortality are more willing to believe stories that tell them they can escape death and live forever. So here's an example: One recent study took two groups of agnostics, that is people who are undecided in their religious beliefs. Now, one group was asked to think about being dead. The other group was asked to think about being lonely. They were then asked again about their religious beliefs. Those who had been asked to think about being dead were afterwards twice as likely to express faith in God and Jesus. Twice as likely. Even though the before they were all equally agnostic. But put the fear of death in them, and they run to Jesus.

　　Now, this shows that reminding people of death biases them to believe, regardless of the evidence, and it works not just for religion, but for any kind of belief system that promises immortality in some form, whether it's becoming famous or having children or even nationalism, which promises you can live on as part of a greater whole. This is a bias that has shaped the course of human history.

　　生死自知

　　Now, the theory behind this bias in the over 400 studies is called terror management theory, and the idea is simple. It's just this. We develop our worldviews, that is, the stories we tell ourselves about the world and our place in it, in order to help us manage the terror of death. And these immortality stories have thousands of different manifestations, but I believe that behind the apparent diversity there are actually just four basic forms that these immortality stories can take. And we can see them repeating themselves throughout history, just with slight variations to reflect the vocabulary of the day. Now I'm going to briefly introduce these four basic forms of immortality story, and I want to try to give you some sense of the way in which they're retold by each culture or generation using the vocabulary of their day.

　　Now, the first story is the simplest. We want to avoid death, and the dream of doing that in this body in this world forever is the first and simplest kind of immortality story, and it might at first sound implausible, but actually, almost every culture in human history has had some myth or legend of an elixir of life or a fountain of youth or something that promises to keep us going forever. Ancient Egypt had such myths, ancient Babylon, ancient India. Throughout European history, we find them in the work of the alchemists, and of course we still believe this today, only we tell this story using the vocabulary of science. So 100 years ago, hormones had just been discovered, and people hoped that hormone treatments were going to cure aging and disease, and now instead we set our hopes on stem cells, genetic engineering, and nanotechnology. But the idea that science can cure death is just one more chapter in the story of the magical elixir, a story that is as old as civilization. But betting everything on the idea of finding the elixir and staying alive forever is a risky strategy. When we look back through history at all those who have sought an elixir in the past, the one thing they now have in common is that they're all dead.

　　So we need a backup plan, and exactly this kind of plan B is what the second kind of immortality story offers, and that's resurrection. And it stays with the idea that I am this body, I am this physical organism. It accepts that I'm going to have to die but says, despite that, I can rise up and I can live again. In other words, I can do what Jesus did. Jesus died, he was three days in the [tomb], and then he rose up and lived again. And the idea that we can all be resurrected to live again is orthodox believe, not just for Christians but also Jews and Muslims. But our desire to believe this story is so deeply embedded that we are reinventing it again for the scientific age, for example, with the idea of cryonics. That's the idea that when you die, you can have yourself frozen, and then, at some point when technology has advanced enough, you can be thawed out and repaired and revived and so resurrected. And so some people believe an omnipotent god will resurrect them to live again, and other people believe an omnipotent scientist will do it.

　　But for others, the whole idea of resurrection, of climbing out of the grave, it's just too much like a bad zombie movie. They find the body too messy, too unreliable to guarantee eternal life, and so they set their hopes on the third, more spiritual immortality story, the idea that we can leave our body behind and live on as a soul. Now, the majority of people on Earth believe they have a soul, and the idea is central to many religions. But even though, in its current form, in its traditional form, the idea of the soul is still hugely popular, nonetheless we are again reinventing it for the digital age, for example with the idea that you can leave your body behind by uploading your mind, your essence, the real you, onto a computer, and so live on as an avatar in the ether.

　　But of course there are skeptics who say if we look at the evidence of science, particularly neuroscience, it suggests that your mind, your essence, the real you, is very much dependent on a particular part of your body, that is, your brain. And such skeptics can find comfort in the fourth kind of immortality story, and that is legacy, the idea that you can live on through the echo you leave in the world, like the great Greek warrior Achilles, who sacrificed his life fighting at Troy so that he might win immortal fame. And the pursuit of fame is as widespread and popular now as it ever was, and in our digital age, it's even easier to achieve. You don't need to be a great warrior like Achilles or a great king or hero. All you need is an Internet connection and a funny cat. (Laughter) But some people prefer to leave a more tangible, biological legacy -- children, for example. Or they like, they hope, to live on as part of some greater whole, a nation or a family or a tribe, their gene pool. But again, there are skeptics who doubt whether legacy really is immortality. Woody Allen, for example, who said, "I don't want to live on in the hearts of my countrymen. I want to live on in my apartment."

　　So those are the four basic kinds of immortality stories, and I've tried to give just some sense of how they're retold by each generation with just slight variations to fit the fashions of the day. And the fact that they recur in this way, in such a similar form but in such different belief systems, suggests, I think, that we should be skeptical of the truth of any particular version of these stories. The fact that some people believe an omnipotent god will resurrect them to live again and others believe an omnipotent scientist will do it suggests that neither are really believing this on the strength of the evidence. Rather, we believe these stories because we are biased to believe them, and we are biased to believe them because we are so afraid of death.

　　So the question is, are we doomed to lead the one life we have in a way that is shaped by fear and denial, or can we overcome this bias? Well the Greek philosopher Epicurus thought we could. He argued that the fear of death is natural, but it is not rational. "Death," he said, "is nothing to us, because when we are here, death is not, and when death is here, we are gone." Now this is often quoted, but it's difficult to really grasp, to really internalize, because exactly this idea of being gone is so difficult to imagine. So 2,000 years later, another philosopher, Ludwig Wittgenstein, put it like this: "Death is not an event in life: We do not live to experience death. And so," he added, "in this sense, life has no end."

　　So it was natural for me as a child to fear being swallowed by the void, but it wasn't rational, because being swallowed by the void is not something that any of us will ever live to experience.

　　Now, overcoming this bias is not easy because the fear of death is so deeply embedded in us, yet when we see that the fear itself is not rational, and when we bring out into the open the ways in which it can unconsciously bias us, then we can at least start to try to minimize the influence it has on our lives.

　　Now, I find it helps to see life as being like a book: Just as a book is bounded by its covers, by beginning and end, so our lives are bounded by birth and death, and even though a book is limited by beginning and end, it can encompass distant landscapes, exotic figures, fantastic adventures. And even though a book is limited by beginning and end, the characters within it know no horizons. They only know the moments that make up their story, even when the book is closed. And so the characters of a book are not afraid of reaching the last page. Long John Silver is not afraid of you finishing your copy of "Treasure Island." And so it should be with us. Imagine the book of your life, its covers, its beginning and end, and your birth and your death. You can only know the moments in between, the moments that make up your life. It makes no sense for you to fear what is outside of those covers, whether before your birth or after your death. And you needn't worry how long the book is, or whether it's a comic strip or an epic. The only thing that matters is that you make it a good story.

　　Thank you.