0:00 Every single cell in your body is replaced over about seven years.0:05 So are you—physically—the same person you were in 2017?0:09 And if the answer is no, then who is?0:12 Exactly!0:13 Last week we were wrestling with being a brain in a vat, questioning if the outside world is real.0:21 This is so much worse.0:23 This question makes me wonder if the inside world is real.0:27 The call is coming from inside the house.0:31 It always is.0:32 The fundamental problem isn't proving the world exists, it's proving you do.0:38 Okay, let's start with the classic.0:41 The Ship of Theseus.0:42 Lay it out for me.0:44 It's an ancient Greek thought experiment.0:47 The hero Theseus has a ship.0:49 Over the years, as the wooden planks rot, they're replaced one by one.0:55 Eventually, every single original plank has been swapped out for a new one.1:01 So the question is—is it still the Ship of Theseus?1:05 That's the first question.1:07 But then it gets a twist.1:10 What if you saved all the old, rotten planks...1:13 and you used them to build another ship?1:17 Oh, no.1:17 So now you have two ships.1:19 The repaired one in the harbor, and the one built from all the original parts.1:26 Which one is the real one?1:28 And there is no clean answer.1:30 Some philosophers say the repaired one, because it has continuous history.1:36 Others say the reassembled one has the original material identity.1:41 This isn't just a puzzle about boats, is it?1:45 This is the seven-year cell replacement thing.1:49 I am the repaired ship.1:51 My parts have all been swapped out.1:53 You are.1:54 So if you're not your physical parts, what are you?1:58 The obvious next step is memory.2:01 You are the person who remembers being you.2:04 That feels right.2:06 I'm me because I remember my childhood, what I had for breakfast, our conversation last week about vats.2:14 That continuity feels like identity.2:17 But what about an amnesiac?2:19 Someone who suffers a head injury and loses all their memories.2:24 Are they no longer the same person?2:27 Their family would certainly say they are.2:31 But they wouldn't feel like it.2:33 To them, they'd be a stranger.2:35 And what about false memories?2:38 We know the brain can create convincing memories of events that never happened.2:44 If your identity is based on a story, what if the story is fiction?2:50 Wait—so if I'm not my body, and I'm not my memories...2:54 what's left?2:55 My consciousness?2:56 The little voice in my head that's currently freaking out?3:01 The stream of consciousness.3:03 The feeling of being you, right now.3:06 But that stream gets interrupted.3:09 Every single night.3:11 When you're asleep.3:12 Or under anesthesia for surgery.3:15 Does "you" stop existing?3:17 And does a new "you" get created in the morning?3:21 It feels continuous to us, but that's just a trick of memory—which we've already established is unreliable.3:29 This is a nightmare.3:31 There's no "thing" to hold on to.3:34 It's not the body, it's not the memories, it's not even the continuous conscious experience.3:41 So what the hell am I?3:43 Is there anything there at all?3:45 That is the abyss you stare into when you take this question seriously.3:51 The feeling of "I" is the most powerful and self-evident experience we have.3:57 But the moment you try to grab it, your hand closes on smoke.4:02 So all the things we build our lives around—our name, our reputation, our promises, our love for people—it's all built on a foundation of...4:14 smoke?4:14 Or maybe the mistake is looking for a "thing" in the first place.4:19 An object called "me." Maybe identity isn't a noun.4:24 What else could it be?4:25 A verb.4:26 An action.4:27 A process.4:28 The philosopher Daniel Dennett talks about the self as a "center of narrative gravity." It’s not a physical thing, but a kind of abstract point that all the stories of your life orbit around.4:43 The self is the story being told.4:46 A story being told...4:47 but who's the narrator?4:49 And who's the audience?4:51 I feel like we just replaced one ghost with another.4:55 Perhaps.4:56 But it shifts the question.4:58 It suggests "you" aren't a thing to be found, but an act to be performed.5:04 You are what you do.5:06 Continuously.5:07 An act to be performed.5:09 A verb, not a noun.5:10 I'm going to be sitting with that for a while.5:14 Is who I am just something I'm doing?5:17 An event that's just… happening?
