Speaker 1: Although every cell in your body changes such that you
Speaker 1: are never again the same person physically, and your neural
Speaker 1: networks change every hour of your life as you absorb
Speaker 1: new experiences. Why do you have an illusion of consistency,
Speaker 1: as though you're the same person you were a week
Speaker 1: ago or a year ago. What does this have to
Speaker 1: do with the mythical watercraft of the Greek demigod Theseus?
Speaker 1: What is the end of history illusion? And why do
Speaker 1: you go through so much trouble to make things comfortable
Speaker 1: for your future self even though you don't know that
Speaker 1: person and you can be guaranteed that that person is
Speaker 1: not going to feel the same way you do now.
Speaker 1: And if there were an afterlife, what age would your
Speaker 1: deity dial you to for living out eternity? Welcome to
Speaker 1: Inner Cosmos with me David Eagleman. I'm a neuroscientist and
Speaker 1: an author at Stanford and in these episodes we dive
Speaker 1: deeply into our three pound universe to uncover some of
Speaker 1: the most surprising aspects of our lives. Today, we're going
Speaker 1: to talk about the notion of having a self and
Speaker 1: what that has to do with our memory. And this
Speaker 1: is a big topic, so we're going to do this
Speaker 1: in two parts. Today, we're going to talk about how
Speaker 1: and why we think of ourselves as lasting through time
Speaker 1: and what that has to do with our memories. And
Speaker 1: in next week's episode, part two, I'm going to talk
Speaker 1: with my colleague, neuroscientist Michael Levin, one of the most
Speaker 1: energized and original thinkers in the field, and I'm going
Speaker 1: to talk with him about the way which memories can
Speaker 1: be thought of like little creatures of their own that
Speaker 1: carry messages in a bottle from one version of you
Speaker 1: to the next. So for today, let's start in ancient Greece,
Speaker 1: where the historian Bluetarch wrote about a tough puzzle that
Speaker 1: had been floating around in the Greek philosopher circles, and
Speaker 1: they were all arguing about it. The puzzle was this,
Speaker 1: imagine the ship of Theseus. Theseus was the hero in
Speaker 1: Greek mythology who slayed the minotaur. The idea is that
Speaker 1: Theseus and his crew of Athenians sail back from Crete
Speaker 1: and dock his wonderful ship. But then the ship sits
Speaker 1: in harbor for a long time and one of the
Speaker 1: planks starts to rot, so it gets replaced with new
Speaker 1: and stronger timber, and then that happens with another plank
Speaker 1: on the ship, and another, and eventually, with enough time,
Speaker 1: the entire ship gets replaced, meaning that a single plank
Speaker 1: is the same as what it was when the ship
Speaker 1: first docked. And the question is is it the same
Speaker 1: ship of Theseus or is it not his ship anymore?
Speaker 1: Because every single part has been replaced. Plutarch suggested that
Speaker 1: half the philosophers in Greece argue the ship is still
Speaker 1: the same ship because it retains its identity despite the
Speaker 1: changes to its parts, and the other half of philosophers,
Speaker 1: he suggested, argued that the ship is not the same
Speaker 1: ship because no part of it is the same. So
Speaker 1: for thousands of years, the Ship of Theseus has been
Speaker 1: a thought experiment that surfaces these tough questions about identity
Speaker 1: and change. By the way, there are lots of variants
Speaker 1: on this. My father had an axe in the garage,
Speaker 1: and he would always hold it up and tell me
Speaker 1: this was actually George Washington's axe. Oh, but the handle
Speaker 1: has been replaced twelve times and the axe head has
Speaker 1: been replaced for times. It was obviously a joke, but
Speaker 1: it got me thinking from a young age about the
Speaker 1: nature of identity in the face of change. Does something
Speaker 1: retain its identity if all departs change? Now, why would
Speaker 1: a neuroscience podcast care about the Ship of Theseus or
Speaker 1: George Washington's acts. It's because that kind of wholesale replacement
Speaker 1: is precisely what's happening to your brain and your entire body.
Speaker 1: A big part of the mystery of selfhood has to
Speaker 1: do with the fact that all the pieces and parts
Speaker 1: that make up you are constantly turning over. Your body
Speaker 1: is built out of thirty trillion cells, and this is
Speaker 1: just cellular stuff. Every bit of the cells has a lifetime.
Speaker 1: Most of the cells die or subdivide at some point.
Speaker 1: But even those cells that stick around your whole life
Speaker 1: and don't divide, like your neurons, they're totally different every
Speaker 1: few years. Why because brain cells aren't made out of
Speaker 1: something stable like metal or cement. Instead, they're made out
Speaker 1: of the basic proteins and lipids and other molecules that
Speaker 1: make up any cell in the body, and those things
Speaker 1: aren't particularly stable. So every single neuron and every cell
Speaker 1: in your body is like the Ship of Theseus. Every
Speaker 1: part of it is getting rebuilt all the time, one
Speaker 1: planket a time, or in this case one molecule at
Speaker 1: a time. The pieces and parts of the cell have
Speaker 1: no meaningful stability, and so a big part of all
Speaker 1: that cellular machinery is simply building and rebuilding and rebuilding,
Speaker 1: and in this way everything gets replaced. So who you
Speaker 1: are physically changes all the time, and the question is
Speaker 1: how does your self stay intact over this changing substrate.
Speaker 1: The answer is it's not clear that it does. But
Speaker 1: cognitively you have this illusion of stability. You are one being.
Speaker 1: You've spent your whole life with a fixed history, as in,
Speaker 1: I grew up here, here's my name, this was my hometown,
Speaker 1: these are my parents. This is how my trajectory in
Speaker 1: life has unfolded, leading me from here to there to there.
Speaker 1: And so we tend to hold the impression that our
Speaker 1: identities are something very stable, but in fact who you
Speaker 1: are drifts in this light. It's always struck me as
Speaker 1: funny to think about the notion of an afterlife, because
Speaker 1: what age would you be Depending on when you get there,
Speaker 1: you might be a very different person than you were
Speaker 1: even five years before that. And so all this inspired
Speaker 1: me to write a short story that's published in my
Speaker 1: book Some sum and I'm going to read that story
Speaker 1: to illustrate the questions of this episode. The story is
Speaker 1: called Prism. God resolved at the outset that he wanted
Speaker 1: every human to partippaid in the afterlife, but the plans
Speaker 1: weren't thought out to completion, and immediately he began to
Speaker 1: run up against some confusion about age. How old should
Speaker 1: each person be in the afterlife. Should this grandmother exist
Speaker 1: here at her age of death, or should she be
Speaker 1: allowed to live as a young woman, recognizable to her
Speaker 1: first lover but not to her granddaughter. He decided it
Speaker 1: was unfair to keep people the age they were at
Speaker 1: the end of their lives, when much of their beauty
Speaker 1: and alacrity had been worn down. Allowing everyone to live
Speaker 1: as a young adult proved an unviable solution, because the
Speaker 1: afterlife quickly degenerated into unbounded sexual pursuits, and at middle
Speaker 1: ages they talked only about their children and mortgages, making
Speaker 1: conversations in the afterlife. Tedious God finally landed on an
Speaker 1: ingenious solution while watching light diffract through a prism. So
Speaker 1: when you arrive here, you are split into your multiple
Speaker 1: selves at all possible ages. The you that existed as
Speaker 1: a single identity is now all ages at once. These
Speaker 1: pieces of you no longer get old, but remain ageless
Speaker 1: into perpetuity. The ewes have transcended time. This takes them
Speaker 1: getting used to The different beams of you might run
Speaker 1: into each other at the grocery store, like separate people
Speaker 1: do in earth life. Your seventy six year old self
Speaker 1: may revisit his favorite creek and run into your eleven
Speaker 1: year old self. Your twenty eight year old self may
Speaker 1: break up with a lover and a diner and notice
Speaker 1: your thirty five year old self visiting that spot, lingering
Speaker 1: on the air of regret hanging over the empty seat. Typically,
Speaker 1: the different youws are happy to see each other because
Speaker 1: they possess the same name in a shared history. But
Speaker 1: the ewes are more critical of yourselves than they are
Speaker 1: of others, and so each you quickly identifies habits that
Speaker 1: get under your skin. It's a fact of the afterlife.
Speaker 1: Don't be surprised to discover that after decomposition into your
Speaker 1: different ages, the different us tend to drift apart. You
Speaker 1: discover that the you of eight years old has less
Speaker 1: than common than expected with the U of thirty two
Speaker 1: and the U of sixty four. The eighteen year old
Speaker 1: you finds more in common with other eighteen year olds
Speaker 1: than with your seventy three year old you. The seventy
Speaker 1: three year old you doesn't mind a bit seeking out
Speaker 1: meaningful conversations with others of the same generation. Beyond the name,
Speaker 1: the us have little else in common, but don't lose hope.
Speaker 1: The shared resume of life, parents, birthplace, hometown, school, years,
Speaker 1: first kiss has a magnetic nostalgic pull. So once in
Speaker 1: a while, the different yous organize a gathering like a
Speaker 1: family reunion, bringing together all your ages into a single room.
Speaker 1: At these reunions, the middle aged will delightedly pinch the
Speaker 1: cheeks of the young, and the teenagers will politely listen
Speaker 1: to the stories and advice of the elderly. These reunions
Speaker 1: reveal a group of individuals touchingly searching for a common theme.
Speaker 1: They appeal to your name as a unifying structure, but
Speaker 1: they come to realize that the name that existed on earth,
Speaker 1: the you that moved serially through these different identities, was
Speaker 1: like a bundle of sticks from different trees. They come
Speaker 1: to understand with awe the complexity of the compound identity
Speaker 1: that existed on the earth. They conclude with a shudder,
Speaker 1: that the earthly you is utterly lost, unpreserved in the afterlife.
Speaker 1: You were all these ages, they concede, and you were none.
Speaker 1: So we're changing all the time. But why is it
Speaker 1: hard to keep track of these changes. Obviously it's because
Speaker 1: everything in our lives and our biology changes so slowly.
Speaker 1: It's like the hour hand of a clock. You can
Speaker 1: see that it's moved, but you can't see it move.
Speaker 1: In general, we can see change most readily in the
Speaker 1: growth of our children. You look back at photographs from
Speaker 1: a year ago on your phone and you can't believe
Speaker 1: how much things have changed. But it's hard to keep
Speaker 1: track of the changes in yourself. A friend of my
Speaker 1: parents went to his high school reunion, which was taking
Speaker 1: place at a hotel, and he went around looking at
Speaker 1: the different conference rooms to figure out which one was
Speaker 1: the correct class, because they were divided up by decades,
Speaker 1: And he thought he found the right room, but he
Speaker 1: popped his head in and he realized that's completely not
Speaker 1: the right room. All of those are very old people.
Speaker 1: And then he stepped back and looked at the sign
Speaker 1: and realized that indeed this was the correct room, and
Speaker 1: he too must presumably look that old to others, even
Speaker 1: if he still thought of himself as young on the inside.
Speaker 1: So it's hard to keep track of our own changes
Speaker 1: because they happen slowly. But maybe the thing that binds
Speaker 1: your self together across the ever changing physical substrate is
Speaker 1: the one thing you have that remains constant, your memory.
Speaker 1: Memory ties all these versions of you together. Memory serves
Speaker 1: as the thread that weaves through all these transformations, anchoring
Speaker 1: a sense of self. So that sounds very nice, but
Speaker 1: there's a fundamental problem with this, which is that memory
Speaker 1: itself is not stable. It drifts, and I've talked about
Speaker 1: this in several episodes. Memory is not a faithful, unchanging
Speaker 1: record of the past. It's instead a fragile brain state,
Speaker 1: and it needs to be reactivated and reconstructed each time
Speaker 1: you recall it. And in this process, memories morph, So
Speaker 1: we can't really think of them as an archive. They're
Speaker 1: more of a story which we continually rewrite. And that
Speaker 1: would be fine to keep rewriting a story, except that
Speaker 1: we assume at all times that our memories form the
Speaker 1: core of a stable identity. So let me give an
Speaker 1: example of how memories change Imagine that you and two
Speaker 1: friends were at some rooftop party and you were best
Speaker 1: friends since college, and the night was full of jokes
Speaker 1: and old stories, and you remember feeling grateful for this
Speaker 1: bond that you shared, and you can still picture the
Speaker 1: three of you by the fireplace, vowing to never let
Speaker 1: life pull you apart. But now, a year later, everything
Speaker 1: has changed. Those two guys are now enemies. It all
Speaker 1: fell apart because one of them had an affair with
Speaker 1: the other's girlfriend. So now when you think back on
Speaker 1: that rooftop party, you wonder was there something in the
Speaker 1: way he and the other guy's girlfriend exchanged glances across
Speaker 1: the room? You now think you sort of remember there
Speaker 1: were little stolen looks, there was some subtle tension in
Speaker 1: the air. Did your other friends sense that something was funny?
Speaker 1: Even then, the memory that once felt warm and comforting
Speaker 1: now feels different, like a scene in a movie that
Speaker 1: you're watching for the second time but noticing new things now.
Speaker 1: The past hasn't changed, but your present knowledge of what
Speaker 1: came after that party colors the memory and reshapes it,
Speaker 1: and it makes you question what was really there and
Speaker 1: what you've unconsciously added. Memory is slippery, like that, the
Speaker 1: more you revisit it, the more it shifts and blurs,
Speaker 1: which reminds me of a great quotation from Sigmund Freud
Speaker 1: on this topic. In eighteen ninety six, he wrote a
Speaker 1: letter to to a colleague about quote, the material present
Speaker 1: in the form of memory traces being subjected from time
Speaker 1: to time to a rearrangement in accordance with fresh circumstances,
Speaker 1: to a retranscription. And there's another quotation that I cite
Speaker 1: often from a writer named John Dufresny, who once wrote
Speaker 1: that quote, Memory is a myth making machine. What we
Speaker 1: do is keep revising our past to keep it consistent
Speaker 1: with who we think we are. So here's where we
Speaker 1: are so far. Our biology is always changing, and so
Speaker 1: the thing that crosses time is our memory. But even
Speaker 1: that changes all the time, drifting or warping or disintegrating altogether.
Speaker 1: And as a result, who you are is always on
Speaker 1: the move. Now, I've been speaking as though we're not
Speaker 1: always aware of so much change happening over time, But
Speaker 1: of course we can come to be aware of this
Speaker 1: in some circumstances. For example, when you look back at
Speaker 1: a diary entry that you wrote some years ago, it's
Speaker 1: often surprising how much you've changed, how much the person
Speaker 1: who held that pen is a bit different than who
Speaker 1: you are now. So we do confront this sometimes. But
Speaker 1: what's weird is despite the massive changes that happen in
Speaker 1: our past, we always think that there will be little
Speaker 1: change in the future. We've changed a lot up until now,
Speaker 1: but now we've settled into place and there won't be
Speaker 1: much change from here. And this is a cognitive illusion
Speaker 1: known as the end of history illusion. In other words,
Speaker 1: we can recognize significant changes in ourselves when we think
Speaker 1: about our past, but we underestimate how much we're going
Speaker 1: to change in the future. We acknowledge that we've grown
Speaker 1: or evolved, but we incorrectly assume that who we are
Speaker 1: right now is pretty close to our final or mature
Speaker 1: version of ourselves. This end of history illusion was first
Speaker 1: studied by psychology just like Daniel Gilbert and his colleagues,
Speaker 1: and they surveyed people on their values and their preferences,
Speaker 1: their personality traits, their life goals, and across the board.
Speaker 1: They found that people consistently believe that they've undergone more
Speaker 1: change in the past than they will in the future.
Speaker 1: But of course it's an illusion because change is a
Speaker 1: continuous process. In other words, if I ask you now
Speaker 1: if you've essentially finished changing in life, if you're likes
Speaker 1: and personality have settled, you'll say yeah. But if I
Speaker 1: track you down and ask you again in five years,
Speaker 1: you'll say, actually, the past five years did hold a
Speaker 1: lot of change for me, but now I've finally arrived
Speaker 1: at my stable self. And it's the same story if
Speaker 1: I survey you five years after that. And this is
Speaker 1: problematic because, for example, we're always trying to predict our
Speaker 1: future emotions. You think, oh, if I get that job promotion,
Speaker 1: or if I'm in this relationship, or if I have kids,
Speaker 1: or if I don't have kids, this will make me happy.
Speaker 1: Or if I lose this job and I have to
Speaker 1: find a new one, that's going to make me miserable.
Speaker 1: This is what psychologists call affective forecasting, where we project
Speaker 1: how we think we're going to feel, but it's based
Speaker 1: on your current limited knowledge about the world, and that
Speaker 1: might change. So why do we have an end of
Speaker 1: history illusion. Well, presumably it's because it's easier for us
Speaker 1: to see the past changes because we have memories and
Speaker 1: experiences to draw from, but future changes are hidden in
Speaker 1: the mists of the future. We don't know what they are,
Speaker 1: so let me give you some concrete examples of this.
Speaker 1: Think about the way we have our career goals. As
Speaker 1: a thirty year old, you might look back and realize
Speaker 1: your career aspirations have changed, maybe significantly, from the time
Speaker 1: you were twenty, but you might assume that your current
Speaker 1: career goals are unlikely to change much in the next
Speaker 1: ten years, even though lots of people shift career paths
Speaker 1: or professional interests throughout life. Or think about your music
Speaker 1: preferences you are older. You may recognize that your taste
Speaker 1: in music has evolved since your teenage years. Maybe you
Speaker 1: went from popper rock to maybe jazz or classical. But
Speaker 1: despite that, you're likely to believe that your current musical
Speaker 1: preferences are going to remain stable for the rest of
Speaker 1: your life, even though your musical tastes are going to
Speaker 1: keep evolving with exposure to new genres and bands and
Speaker 1: instruments that don't even exist yet. We're thinking about friendships.
Speaker 1: In your early twenties, you might reflect on how your
Speaker 1: circle of friends has changed from high school to college.
Speaker 1: There's a big shift in relationships there, but you might
Speaker 1: simultaneously feel certain that the college friends you have now
Speaker 1: are going to be your closest companions for life. That's
Speaker 1: a totally understandable position, but it underestimates how friendships shift
Speaker 1: as you enter different life stages, like when you start
Speaker 1: a family or you move to a new city. The
Speaker 1: same reasoning applies to everything, So take hobbies and interest
Speaker 1: When you're in your fish, you notice that you've taken
Speaker 1: up new hobbies and given up old ones over the years,
Speaker 1: but you'll generally believe that your current interests will remain
Speaker 1: consistent for the coming decades, when in fact, new hobbies
Speaker 1: and interests will still emerge. You just can't see that
Speaker 1: because they're ensconced in the dark forest of the future.
Speaker 1: Possibly there's some new technology that you're going to be
Speaker 1: obsessed with that hasn't even been invented or named yet. Okay,
Speaker 1: And the one that's really hard for us to admit
Speaker 1: to is future changes in our political values and social beliefs,
Speaker 1: and possibly religious beliefs. When you look back on any
Speaker 1: of your beliefs from a decade ago, you can sometimes
Speaker 1: see there have been some changes. But again, we tend
Speaker 1: to assume that our current values are now locked into
Speaker 1: place for the rest of our lives. We all fail
Speaker 1: to anticipate that our worldview is going to continue to
Speaker 1: get reshaped by life experiences, by new information, by changing
Speaker 1: social contexts. In a decade, we might not be precisely
Speaker 1: who we are right now. Now, this whole end of
Speaker 1: history illusion wouldn't really matter for our lives, except that
Speaker 1: it affects how we make decisions. Because so much of
Speaker 1: what you do is in service to the assumed future you.
Speaker 1: You suffer through courses and trainings now to make things
Speaker 1: better for your future you. You sweat through a workout
Speaker 1: so your future you will have a better body. You
Speaker 1: put your money into retirement plans to make sure that
Speaker 1: the future you has the resources that you predict that
Speaker 1: stranger will need. The difficulty simply is that we're not
Speaker 1: good predictors. You don't really know who that person is.
Speaker 1: That person shares your name and your history, but the
Speaker 1: fact is that person might be very different than the
Speaker 1: current you. So you're donating your retirement money for this
Speaker 1: future person that you can essentially guarantee will be not
Speaker 1: who you currently believe. That person might vote for the
Speaker 1: other political party, the what you would never vote for
Speaker 1: and yet you're slaving away and handing over all your
Speaker 1: money to that maniac. And you also do stuff assuming
Speaker 1: the best about your future self, but sometimes that's not
Speaker 1: useful either. We tend to assume that our future self
Speaker 1: will be more motivated or disciplined than we are today.
Speaker 1: So because of that, you might sign up for an
Speaker 1: expensive gym membership believing that you'll be more committed in
Speaker 1: the future, but then you don't really follow through. Your
Speaker 1: future self isn't as on board with the plan as
Speaker 1: your past self believed it would be. As a related example,
Speaker 1: I'm chronically over committed because at every moment I assume
Speaker 1: that my future self is going to be less busy
Speaker 1: than I am now, and so I say yes to
Speaker 1: future invitations or obligations like taking on big new projects
Speaker 1: or attending multiple social events, And when the time arrives,
Speaker 1: my future me wishes that my past me hadn't over committed.
Speaker 1: And more generally, we fall victim to lots of planning fallacies.
Speaker 1: We underestimate how long it's going to take to complete
Speaker 1: some task. You might think cool, I can knock that
Speaker 1: thing out in a week, and then you find that
Speaker 1: it takes twice as long now. That happens because we
Speaker 1: typically fail to correctly predict all the possible setbacks and
Speaker 1: complexities that will run into in the future. My favorite
Speaker 1: example of a planning fallacy is with a gentleman named
Speaker 1: James Murray who in eighteen seventy eight set out to
Speaker 1: write the for the English Dictionary, and the idea was
Speaker 1: to capture all the words in the English speaking world
Speaker 1: and give definitions for all of their various shades of meaning.
Speaker 1: And this seemed like a big undertaking, but not big
Speaker 1: enough that he couldn't complete it in a few years.
Speaker 1: So he worked on this for thirty six years until
Speaker 1: he died, and then several editors took up the mantle
Speaker 1: after him, and the first edition of the Oxford English
Speaker 1: Dictionary was finally completed seventy years after he began. He
Speaker 1: totally misapprehended the size of the project, and if I
Speaker 1: were here, I presumably would have done the same. So
Speaker 1: as a result of this sort of planning fallacy, we're
Speaker 1: constantly making decisions that our future selves are going to
Speaker 1: regret or disagree with. Why. It's not because we're idiots now,
Speaker 1: but instead because our circumstances and our preferences and our
Speaker 1: priorities are to change over time. Okay, so let me
Speaker 1: zoom back out to the big picture. We are creatures
Speaker 1: who live and change through time, but we're yoked with
Speaker 1: this illusion that we are unchanging, and so we misremember
Speaker 1: our past and we work hard for future versions of
Speaker 1: ourselves who we assume will be like us, but they
Speaker 1: may not be. And by the way, there are all
Speaker 1: kinds of complex relationships between your future self and your
Speaker 1: past self through time, so it gets pretty crowded. Your
Speaker 1: past self says, oh, I'm not gonna worry about my
Speaker 1: future self, and your future self looks back and says,
Speaker 1: what a jerk like. When people make the decision in
Speaker 1: the short term to postpone their education or splurge on
Speaker 1: some overpriced thing, and then your future self thinks, dang,
Speaker 1: I wish I'd gone to that class or spent my
Speaker 1: money on something more meaningful or necessary. This comes up
Speaker 1: for many people. In terms of retirement savings. People will
Speaker 1: make the decision to spend now rather than save for
Speaker 1: their future self. They keep thinking, oh, I'll start saving later,
Speaker 1: But then as retirement approaches, your future self feels mad
Speaker 1: at your past self and wished as you had started
Speaker 1: saving earlier, and I suspect this is true. Anytime we
Speaker 1: choose instant gratification over long term goals, our future selves
Speaker 1: look back and they're mad about it. And all this
Speaker 1: highlights the challenge of balancing short term desires with long
Speaker 1: term outcomes. In other words, your self in the moment
Speaker 1: now versus yourself in the future. So let's wrap up.
Speaker 1: In the next episode, Part two, we're going to dive
Speaker 1: deeper into all these paradoxes of the self by talking
Speaker 1: with my colleague neuroscientist Mike Levin, who wrote a recent
Speaker 1: paper in which he pointed out that quote if we
Speaker 1: do not change, learning and growth is impossible. If we
Speaker 1: do change, does not the current self cease to exist
Speaker 1: in an important sense end quote. So let's summarize where
Speaker 1: we got in this episode. We began by looking at
Speaker 1: the illusion of continuity, and we use the ancient thought
Speaker 1: experiment of the ship of Theseus, where one plank of
Speaker 1: the ship gets replaced at a time, and we can
Speaker 1: ask is it still the ship of theseus after every
Speaker 1: plank has been replaced. We looked at this question because
Speaker 1: we are always surfing on top of constant physical changes,
Speaker 1: and yet we perceive ourselves as consistent over time. The
Speaker 1: planks and theseus's ship are the cells and molecules in
Speaker 1: your body, and this foregrounds the question about what makes
Speaker 1: you the same person over time. We asked the question
Speaker 1: of whether we can really say that memory is the
Speaker 1: thread holding identity together, because the truth is that memory
Speaker 1: is far from reliable. It's constantly being rewritten. And finally,
Speaker 1: we touched on a cognitive bias known as the end
Speaker 1: of history illusion, which is where we massively underestimate how
Speaker 1: much we're going to change in the future, even though
Speaker 1: we're aware that we've changed in the past. We tend
Speaker 1: to believe that our current tastes and values and personalities
Speaker 1: are going to remain consistent from here on out, even
Speaker 1: though we keep on changing throughout our lives. So you
Speaker 1: can't actually be your past self. But as we'll see
Speaker 1: in part two next week, we constantly try to reconstruct
Speaker 1: that person. We constantly try to revivify that past self
Speaker 1: based on the evidence provided by reinterpreting the clues that
Speaker 1: are left by them. In other words, the memories that
Speaker 1: are buried in the neural network. In this view, memories
Speaker 1: are like a message in a bottle thrown from your
Speaker 1: present self into the ocean for someone to find, and
Speaker 1: that someone is a future you who you don't necessarily know.
Speaker 1: Go to Eagleman dot com slash podcast for more information
Speaker 1: and to find further reading. Send me an email at
Speaker 1: podcasts at eagleman dot com with questions or discussion and
Speaker 1: check out Subscribe to Inner Cosmos on YouTube for videos
Speaker 1: of each episode and to leave comments until next time.
Speaker 1: I'm David Eagleman and this is Inner at Cosmos.