Star Trek–style teleportation may one day become a reality. You step into the transporter, which instantly scans your body and brain, vaporizing them in the process. The information is transmitted to Mars, where it is used by the receiving station to reconstitute your body and brain exactly as they were on Earth. You then step out of the receiving station, slightly dizzy, but pleased to arrive on Mars in a few minutes, as opposed to the year it takes by old-fashioned spacecraft.

But wait. Do you really step out of the receiving station on Mars? Someone just like you steps out, someone who apparently remembers stepping into the transporter on Earth a few minutes before. But perhaps this person is merely your replica—a kind of clone or copy. That would not make this person you: in Las Vegas there is a replica of the Eiffel Tower, but the Eiffel Tower is in Paris, not in Las Vegas. If the Eiffel Tower were vaporized and a replica instantly erected in Las Vegas, the Eiffel Tower would not have been transported to Las Vegas. It would have ceased to exist. And if teleportation were like that, stepping into the transporter would essentially be a covert way of committing suicide. Troubled by these thoughts, you now realize that “you” have been commuting back and forth to Mars for years . . .

So which is it? You are preoccupied with a question about your survival: Do you survive teleportation to Mars? A lot hangs on the question, and it is not obvious how to answer it. Teleportation is just science fiction, of course; does the urgent fictional question have a counterpart in reality? Indeed it does: Do you, or could you, survive death?

Teeming hordes of humanity adhere to religious doctrines that promise survival after death: perhaps bodily resurrection at the Day of Judgment, reincarnation, or immaterial immortality. For these people, death is not the end.

Some of a more secular persuasion do not disagree. The body of the baseball great Ted Williams lies in a container cooled by liquid nitrogen to -321 degrees Fahrenheit, awaiting the Great Thawing, when he will rise to sign sports memorabilia again. (Williams’s prospects are somewhat compromised because his head has apparently been preserved separately.) For the futurist Ray Kurzweil, hope lies in the possibility that he will be uploaded to new and shiny hardware—as pictures are transferred to Facebook’s servers—leaving his outmoded biological container behind.

Isn’t all this a pipe dream? Why isn’t “uploading” merely a way of producing a perfect Kurzweil-impersonator, rather than the real thing? Cryogenic storage might help if I am still alive when frozen, but what good is it after I am dead? And is the religious line any more plausible? “Earth to earth, ashes to ashes, dust to dust” hardly sounds like the dawn of a new day. Where is—as the Book of Common Prayer has it—the “sure and certain hope of the Resurrection to eternal life”? If a forest fire consumes a house and the luckless family hamster, that’s the end of them, presumably. Why are we any different?

Philosophers have had a good deal of interest to say about these issues, under the unexciting rubric of “personal identity.” Let us begin our tour of some highlights with a more general topic: the survival, or “persistence,” of objects over time.

Physical objects (including plants and animals) typically come into existence at some time, and cease to exist at a later time, or so we normally think. For example, a cottage might come into existence when enough beams and bricks are assembled, and cease to exist a century later, when it is demolished to make room for a McMansion. A mighty oak tree began life as a tiny green shoot, or perhaps an acorn, and will end its existence when it is sawn into planks.

The cottage and the oak survive a variety of vicissitudes throughout their careers. The house survived Hurricane Irene, say. That is, the house existed before Irene and also existed after Irene. We can put this in terms of “identity”: the house existed before Irene and something existed after Irene that was identical to the house.

If you don’t have to go where your soul goes, or where your body goes, then you go where your mind goes.

Explaining what survival amounts to in terms of identity helps to clarify the notion, but it is potentially confusing. Suppose your house burns down and you build an identical house in its place. That is not a situation in which your house survives—it’s a situation in which your house is destroyed and a replica is built in its place. Although your original house and the replica are identical in the sense that they are very similar, there is another sense in which they are not identical. There are two houses in the story, and in the “numerical” sense of identity two things are never identical. We have the numerical sense in mind when we say that Lady Gaga and Stefani Germanotta are identical: we don’t just mean that Gaga and Germanotta are similar, like your iPhone and my iPhone, or the members of the Scottish band The Proclaimers, who are identical twins. Gaga and Germanotta are not two at all: “they” are one and the same. Survival, then, should be cashed out in terms of numerical identity: you survive some event just in case you exist before the event and someone exists after the event who is numerically identical to you.

Houses can survive repainting and the addition of a porch; they cannot survive being consumed by fire or having their parts scattered. But there are difficult cases. Imagine your ancient family home has been lovingly repaired over the years so that now not a single brick or beam from the original construction remains; they have all been replaced with period bricks and beams from architectural salvage. Has the original house survived? Not an easy question, but only a professional metaphysician would care about the answer. Sentiment aside, it doesn’t much matter whether this is (numerically) identical to the house your grandfather lived in, as opposed to one just like it built on the same spot.

However there is one thing whose survival seems to be of the greatest importance—here I speak for myself—namely me. As we have seen, questions about survival can be put in the language of identity, and since we are persons, philosophers use “personal identity” as a label for the study of the sorts of events we can undergo and survive.

Contemporary discussions of personal identity owe a great deal to the seventeenth-century English philosopher John Locke, whose Essay Concerning Human Understanding contains many fantastic thought experiments of the sort (like the teleportation example) that are staples in the contemporary philosophical literature. Locke’s interest in the topic was motivated by his belief in a Christian afterlife and his suspicion of the then-prevalent idea (deriving from Plato) that we survive death because we have immaterial souls that outlast our bodies. Locke thinks we cannot rule out the view that the Almighty, instead of animating our bodies by uniting them with immaterial souls, has instead just made matter capable of supporting mental lives, not bothering to create immaterial souls at all. Locke’s account of personal identity is designed to make room for the Day of Judgment whether or not there are immaterial souls. “All the great ends of morality and religion,” he wrote, “are well enough secured, without philosophical proofs of the soul’s immateriality.”

It will be easiest to approach Locke’s position by considering some of his arguments (slightly altered) against rival views. So first consider the view that our survival consists in the survival of our immaterial souls: you go where your soul goes. Imagine that the immaterial soul inhabiting your body is, in fact, numerically identical to—the very same soul as—the immaterial soul that inhabited the body of Socrates. You have no memory of any events in ancient Greece, yet on the view that ties our survival to the survival of our souls, Socrates has survived as you. You and Socrates would therefore be one and the same person, like Lady Gaga and Stefani Germanotta, or George Orwell and Eric Blair. But in Locke’s words, “being not conscious of any of Socrates’s actions or thoughts,” could you really be the same person as that snub-nosed Greek? Can you attribute Socrates’ actions to yourself, or think them your own “more than the actions of any other man, that ever existed?” Plainly not, Locke thinks: even if the immaterial soul inhabiting Socrates’s body turns out to be numerically the same soul as the one inhabiting your body, this would not be the discovery that you are identical to Socrates. So our survival does not consist in the survival of immaterial souls.

Could our survival consist instead in the survival of our bodies? If so, the resurrection of the flesh, provided that involves the reassembly of bodies numerically identical to those that once walked the Earth, would secure our survival after death. Locke uses his famous story of the prince and the cobbler to argue that this view is also incorrect. Imagine, he said, “the soul of a prince, carrying with it the consciousness of the prince’s past life,” enters the body of a cobbler “as soon as deserted by his own soul.” That is, the mind or psychology of the prince has been transferred to the body of the cobbler. (That this is accomplished by transferring the prince’s soul is not essential.) For symmetry, we can suppose the mind of the cobbler has gone in the opposite direction, transferred to the body of the prince.

Suppose that before the mind swap Peter the prince wears a crown and Charlie the cobbler wears a cap. After the mind swap, who is the person wearing a cap: Peter or Charlie? Clearly Peter, Locke thinks. The “mind swap” has had the effect of switching the two people: they have swapped bodies, as two people might swap houses. That can seem very plausible: after all, the person in the cobbler’s body will claim he is the prince, will have the prince’s personality, will be able to give detailed answers to questions about the prince’s past experiences, and (presumably) will loudly complain that the humble wizened body of the cobbler does not befit a man of his noble stature. If a palace coup results in the prince’s body being chopped into tiny bits, the person in the cobbler’s body will congratulate himself on his good fortune: according to him, his original body is no more, but he himself lives on. And from Charlie’s point of view, the continued existence of the cobbler’s original body is no comfort at all. (A version of Locke’s example is the central plot line of the children’s book Freaky Friday, now on its third film adaptation.)

Let us recap. You don’t have to go where your immaterial soul goes—not at least if it doesn’t take your mind with it. You don’t have to go where your body goes—not at least if it doesn’t take your mind with it. What does this suggest? That you go where your mind goes or, as Locke puts it, “personal identity consists . . . in the identity of consciousness.”

Locke’s interest in the afterlife was motivated by his suspicion of the idea that we have immaterial souls.

Let us not pause to examine what exactly Locke means by “identity of consciousness” and instead turn to the development of his view by the philosopher Derek Parfit, whose 1984 book Reasons and Persons is partly devoted to defending a “neo-Lockean” theory of personal identity and to extracting some astonishing implications from it.

The basic neo-Lockean idea is that you survive just in case your psychology continues on in roughly the manner it does in ordinary life. Our psychological lives are not a series of unrelated mental events, but form a complex structure. A simple example: you go to the beach and enjoy the experience of basking on the hot sand. At noon you decide to return home at sunset, and this explains why at dusk you gather up your towel. In the evening at home you recall being at the beach, the feeling of the sand on your feet, and so forth. This illustrates what Parfit calls “psychological connectedness,” the sort of relation that holds between your decision to leave and subsequent towel gathering, and between your beach experience and subsequent recollection. We can think of your psychological life from childhood to old age as overlapping stretches of psychological connectedness, like strips of paper glued together to form a much longer strip. Parfit calls this “psychological continuity.” Parfit’s view is that personal identity—our survival or persistence over time—consists in psychological continuity and connectedness.

Actually, that’s a simplification—for a reason that will turn out to be important. Your psychological life could fork or divide, analogous to the long strip of paper being partly cut down the middle, forming a Y-shape. Parfit imagines a not entirely fanciful way this division could come about. Certain psychological capacities are to some extent lateralized in the brain: in most people the left hemisphere is chiefly responsible for language processing, for example. Suppose, though, that your hemispheres are completely symmetrical: if you lost a hemisphere in an accident, you would survive with your basic faculties intact. (Even with this stipulation, you would not survive entirely undiminished: losing a hemisphere would leave you blind in half your visual field, for example.) Now imagine that we divide your brain, transplanting the left hemisphere into a new de-brained body and the right hemisphere into another. Call the person who wakes up with the left hemisphere “Lefty” and the one who wakes up with the right hemisphere “Righty.” Both Lefty and Righty are psychologically connected to and continuous with you: both will claim to be you, to have your memories, your desires, intentions, and so on. If psychological continuity and connectedness are all that matters for personal identity then you are identical to Lefty and also identical to Righty. But from the logic of numerical identity it follows that Lefty is identical to Righty. (Sting and Trudie Styler’s husband are identical, so are Sting and Gordon Sumner, therefore Trudie Styler’s husband and Gordon Sumner are identical.) But surely Lefty isn’t numerically identical to Righty: after the operation there are two people, not one. Hence you cannot be identical both to Lefty and to Righty because the two of them would then be, impossibly, numerically identical to each other. Thus personal identity cannot merely consist in psychological continuity and connectedness. Parfit’s fix is simply to say that personal identity consists in “non-branching” psychological continuity and connectedness: identity is preserved provided one’s psychological life continues in a single line, with no forking.

The neo-Lockean theory sketched so far—somewhat simpler than Parfit’s official view—is admirably suited, as Locke hoped, to securing survival on the other side. To bring you back from death, God does not need to give you an immaterial soul or go to the bother of collecting the atoms that composed your body when you drew your last breath. (As was well known in Locke’s time, the possibility that cannibals consume your corpse poses a problem for the latter route. If your atoms end up in the cannibals’ bodies then God is going to have a hard time resurrecting everyone.)

Granted neo-Lockeanism, all God has to do is ensure that your psychological life continues on in a non-branching way. That could be accomplished by a divine form of teleportation, perhaps in the process replacing your clapped-out body with a new and improved model. “The dead shall be raised incorruptible,” as the Apostle Paul says. Further, God is not needed, at least in theory: Kurzweil’s “uploading” would also do the trick. So the neo-Lockean theory offers something to believers and unbelievers alike.

There’s an ironic twist, though. According to Parfit, neo-Lockeanism shows that survival is nowhere near as important as we think. Return to the case where your brain is divided. On Parfit’s view, you do not survive the operation. Setting aside practical problems (particularly acute if you are married), is the operation to be feared? Suppose you could bribe the nurse to drop one of the hemispheres on the floor. Then only one hemisphere would be successfully transplanted, there would be no forking, and you would survive in a new body. But is it really worth bribing the nurse? If you don’t bribe her, your psychology will flow into the psychologies of two future people; if you do, it will flow into the psychology of only one. Put that way, it seems that the former option should be better than the latter, not worse. By not bribing the nurse, you get psychological connections with a future person twice over.

This and related examples lead Parfit to conclude, “Personal identity is not what matters,” by which he means that survival is only of derivative value: it is valuable only as a means to an end, not as an end in itself. In ordinary life, survival seems to be the quintessential end in itself, but the case where your psychology divides shows otherwise. You do not survive, but nothing of value is lost, so survival is not of fundamental value. Similarly, owning a corkscrew is only of derivative value: if you lose your corkscrew, but Jeeves decides to work for you pro bono, opening your wine and doing much else besides, then although your corkscrew has gone, nothing of value is lost (indeed, life is much more agreeable). So having a corkscrew is not of fundamental value.

The division and other examples show, according to Parfit, that what fundamentally matters is that your psychology flows on, in you or in someone else. But notice that a weak kind of psychological flow between you and others occurs all the time. Friends and family may come to share some of your beliefs and preferences, and sometimes they act to fulfill your plans, as when you ask someone to do you a favor and bring over some milk. What’s more, psychological connections such as these—flows from you to others—usually remain after death, at least to some extent. “Now that I have seen this,” Parfit says, “my death seems to me less bad.” Parfit observes that his position bears some similarity to the Buddhist “no-self” doctrine of anatta, at least on one interpretation. As the philosopher Mark Johnston understands the doctrine in his Surviving Death (2010), “There are no persisting selves worth caring about.”

Survival is nowhere near as important as we think.

Parfit’s route to anatta departs from the assumption that the neo-Lockean view is the correct theory of personal identity. Johnston, however, has been a forceful, albeit sympathetic, critic of this theory over the years, so his argument for the same, no-persisting-selves conclusion is different. It defies easy summary, but one of the main ideas is that the sort of “everyday egocentrism” you (and the rest of us) display, this sense that you are particularly important, can only be justified if you are very special—if you are the unique possessor of what Johnston calls a “superlative self.” But you are not special in this way, and neither is anyone else. The discovery that we are not in any sense deserving of “premium treatment,” Johnston argues, “eliminates the death we feared most.”

Both Parfit and Johnston agree, then, that too much fuss is made about mortality: ceasing to exist is not so terrible. But Johnston thinks that Death has another threat up his sleeve. “I am in hope,” Socrates says in Plato’s Phaedo, “that there is something for us in death, and as was claimed from old, something better for the good than for the bad.” Socrates’ hope will not be in vain if the righteous dead find happiness in Homer’s Elysian Fields, Joseph Smith’s Celestial Kingdom, or some other paradise, but what if there is no such destination?

And even if there is, Johnston thinks that the good couldn’t get there. He argues at length that we aren’t the kinds of things that could survive a journey to the other side: there is no immaterial soul, no sense can be made of bodily resurrection, and neo-Lockeanism is mistaken.

Yet, according to Johnston, Socrates’ hope is not in vain. The truly good, unlike the bad, do survive death. Does he mean that the good survive in some metaphorical sense, as Steve Jobs survives in the iPad? No: he means it literally. If you are truly good, then after you die, there will be someone around who is numerically identical to you.

How does Johnston pull this rabbit out of a seemingly empty hat? Imagine, as we did at the start, that transporter technology has been developed. The question, “Do we survive teleportation?” naturally becomes pressing. Two opposing camps arise. The members of one camp—the Transporters—are convinced that they survive teleportation. For them, teleportation is a convenient means of superfast travel. The Transporters are opposed by the Luddites, who are convinced that teleportation is destruction, slightly ameliorated by the creation of a replica. The Transporters use the new technology to found a forward-looking civilization on Mars, while the Luddites stay here on Earth, boarding buses and pedaling bicycles.

Now can we maintain that one of these two groups is wrong? Could it really be that the Transporters, despite organizing their lives around the assumption that they survive teleportation, are cruelly deluded? Or perhaps the Luddites, despite being quite sure that the transporter is a fancy photocopier that destroys the original in the process of duplicating it, are like people who are irrationally afraid of flying. Johnston argues that there is no asymmetry between the two communities that could explain how one is making such a huge mistake. Somehow, he thinks, we have to find an account of personal identity on which both communities are right. The Transporters are right when they say, “We Transporters can survive teleportation,” and the Luddites are also right when they say, “We Luddites cannot survive teleportation.”

What is it about the Transporters that enables them to survive teleportation, while the Luddites don’t? Well, one clear difference is that a Transporter cares about the person who steps out of the receiving station as himself. If a Transporter learns that when he enters the transporter the person who steps out of the receiving station will win a million dollars, he will eagerly enter. If a Luddite learns the same thing, she will react as if she were told that when she jumps to her death someone else will get a million dollars—she won’t jump, and neither will she enter the transporter. Drastically compressing Johnston’s complex argument, he concludes that this difference in the “pattern of self-concern” makes for a difference in the sorts of events that the members of the two communities can undergo and survive.

A corollary of this is that our natures are mutable, or, as Johnston puts it, “protean,” after the shape-shifting Greek god Proteus. Survival training allows one to survive events that one could not have survived before the training—one might learn how to survive outdoors in extreme cold, for instance. According to Johnston, survival training could have even more dramatic results. If a Luddite child is kidnapped and raised by the Transporters, she undergoes a form of survival training. After being fully assimilated into Transporter culture, with its distinct pattern of self-concern, she is able to survive Teleportation, which she could not have survived before.

One more step, and we will have reached what Johnston grandly calls “A New Refutation of Death.” Consider the Tiger: not particular tigers living in a zoo or in India—Tigger and Shere Khan, say—but the endangered species that is the mascot of Princeton University. The Tiger, Johnston argues, is a “higher-order individual,” an individual that at any time is embodied by more familiar “first-order” tigers, such as Tigger and Shere Khan. Sooner or later the Tiger will be extinct, but its longevity is much greater than that of any “first-order” tiger. When Tigger and Shere Khan die, the Tiger will survive, embodied in the remaining first-order tigers.

To refute death, we need to combine our protean nature with the point about higher-order individuals. Given that we are protean, we can change what sorts of events we can survive by changing our pattern of self-concern. For example, a Transporter is able to survive teleportation because she cares deeply about the person who steps out of the receiving station. And given that the Tiger is a higher-order individual, Humanity or Mankind is a higher-order individual too, transcending individual people as the Tiger transcends Tigger and Shere Khan.

What if someone were truly good, a follower of, per Johnston, “the command of agape or radical altruism,” and cared about everyone as if they were herself? That pattern of self-concern would make her a higher-order individual; not quite Humanity, but something like it. If someone conforms to the demands of agape and regards the interests of others as she regards the interests of herself, then she will survive by being partly embodied by those others. She would then “quite literally, live on in the onward rush of mankind,” Johnston writes.

Both the neo-Lockean view and Johnston’s proteanism about personal identity give us ways we could survive bodily death. For the religiously inclined, neo-Lockeanism explains how the raising of the dead could be accomplished by ensuring that their mental lives flow on in new bodies. For the ungodly, it shows how pursuit of the technology of “uploading” might achieve a similar result. And proteanism offers, if not any kind of practical path to survival after death, at least a glorious vision of a material universe not wholly indifferent to our good deeds.

The two views have something else in common: they both tie our survival closely to our psychology, although in very different ways. Both neo-Lockeanism and proteanism privilege our mental properties over our bodily ones, and to that extent can be seen as distant descendants of Descartes’s dualism, according to which we are essentially “thinking things.”

One might wonder, though, about the wisdom of retaining even these vestigial bits of Cartesianism. Take neo-Lockeanism. If personal identity consists in certain sorts of psychological connections, then you did not come into existence before you had the necessary psychological capacities. By the same token, you cannot survive the loss of these capacities. So, according to neo-Lockeanism, you were never a fetus, and you will cease to exist if Alzheimer’s destroys your mind.

That result should sound odd. You are an animal, a primate like a chimp or a bonobo. If you aren’t, who is the member of the species Homo sapiens sapiens wearing your underwear right now? Someone else? And if you are an animal, then personal identity begins to look rather different. A chimp did not pop into existence after birth: it was present earlier in the womb. And if a chimp has large areas of its brain removed in the interests of science, the living, breathing chimp is still around, despite the fact that its psychological life has been obliterated. The survival of animals over time is not intimately connected to psychology; if we are animals, then neo-Lockeanism is false. Similarly, although less straightforwardly, with proteanism. On the face of it, mere animals are not the sorts of things that can survive bodily death, no matter how much they care for their conspecifics.

The claim that we are animals is not new: it was considered and swiftly rejected by Locke. Now called “animalism,” it has lately experienced something of a revival, due in no small part to Eric Olson’s 1997 book The Human Animal. Unfortunately animalism holds out little prospect for enjoying life beyond the grave. To paraphrase Bertrand Russell, when animals die, they rot.

Animalism, however, does not much affect Parfit’s and Johnston’s arguments for anatta, that there are no persisting selves worth caring about. Parfit’s argument from division goes through as before, since animalism predicts that you do not survive the brain division operation, just as neo-Lockeanism does. And similarly for Johnston’s argument about the absence of “substantial selves,” since animalism has no truck with them either.

It would be optimistic to rest your hopes for an afterlife on philosophy. More promising, though, is the idea that our own survival is greatly over-valued. Philosophy cannot offer immortality, but it might be able to draw the sting of death a little.