Are You Real? — Transcript

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1. 0:00Look at your hand. How many fingers do
2. 0:01you have? You can see them. You can feel
3. 0:04them. You are certain they're there. You
4. 0:06shouldn't be. From inside your own head,
5. 0:09you can't actually prove a single one of
6. 0:11those fingers is real. The same goes for
7. 0:13the hand they're attached to. And the
8. 0:15room around you that feels like it's
9. 0:16just there, whether you look at it or
10. 0:18not. Try it yourself. Right now, find
11. 0:21one piece of evidence that what you're
12. 0:22experiencing is real and not a flawless
13. 0:25imitation of it. You won't be able to.
14. 0:27And the reason why is stranger than it
15. 0:29sounds. Everything you know about the
16. 0:30world arrives the same way. Light hits
17. 0:32your eyes and your brain turns it into
18. 0:35color and shape. Pressure lands on your
19. 0:37skin and becomes the feeling of touch.
20. 0:39Air vibrates and you call it sound. Your
21. 0:42brain takes those raw signals and builds
22. 0:44a picture out of them and that picture
23. 0:46is the only world you will ever actually
24. 0:48meet. You have never once touched
25. 0:50reality directly. You have only ever
26. 0:51touched your brain's version of it. And
27. 0:53that's where it gets strange. If the
28. 0:55only thing you can ever inspect is the
29. 0:57picture in your head, you have no way to
30. 0:58step outside the picture and hold it up
31. 1:00against the real thing. There is no
32. 1:02door. The final stop for every sight,
33. 1:04every sound, every fact you've ever
34. 1:06learned is you, alone, inside your own
35. 1:09skull. Philosophers call this the
36. 1:11egocentric predicament. You are sealed
37. 1:13in. And from the inside, a perfect fake
38. 1:16and the real thing look exactly the
39. 1:19same. You already live through a version
40. 1:20of this. When you dream, all of it feels
41. 1:22completely real while you're inside it.
42. 1:25You're being chased and your legs won't
43. 1:26move like you're running through wet
44. 1:28cement. The ground drops away and you're
45. 1:30falling with nothing to grab onto. Your
46. 1:31teeth crumble and fall out one by one.
47. 1:34And while it's happening, you never once
48. 1:36stop to think any of it is strange.
49. 1:37Inside the dream, that's just how the
50. 1:40world is. [music] And you can't test
51. 1:41your way out of it. If you stop to check
52. 1:43your hands or pinch yourself to be sure,
53. 1:45the dream just produces the hands and
54. 1:47the pinch along with everything else.
55. 1:49Every test you could run is made of the
56. 1:50same dream. You only realize none of it
57. 1:52was real after you wake up, when you
58. 1:54finally have the solid waking world to
59. 1:56hold it against. So, here's the
60. 1:58uncomfortable version. Right now, while
61. 2:00you're awake, what wider world are you
62. 2:02measuring this against? Nearly 400 years
63. 2:04ago, René Descartes sat with that exact
64. 2:06thought and couldn't shake it. If a
65. 2:08dream can feel this convincing from the
66. 2:10inside, then nothing you're sensing in
67. 2:12this moment can prove it isn't one. He
68. 2:14pushed it further and imagined an evil
69. 2:16demon devoted to deceiving him about
70. 2:18everything. The ground, the sky, his own
71. 2:21body. He went hunting for one single
72. 2:23thing that demon couldn't fake. And he
73. 2:25found almost nothing left standing. In
74. 2:271981, the philosopher Hilary Putnam made
75. 2:30the same doubt even harder to escape.
76. 2:32Picture a brain floating in a tank of
77. 2:34fluid, kept alive, wired into a computer
78. 2:37that feeds it electrical signals. The
79. 2:39exact signals a real body would send.
80. 2:41The taste of coffee, the weight of a
81. 2:43blanket, the face of someone it loves.
82. 2:45That brain would feel an entire life. A
83. 2:47childhood, a hometown, a name. And it
84. 2:50would have no way at all to discover the
85. 2:52tank. Because every test it could run,
86. 2:54every pinch, every glance down at its
87. 2:56own hands, would just be more signal
88. 2:58from the same machine. Then, notice the
89. 3:00part that should bother you. From the
90. 3:01inside, that brain's experience would be
91. 3:03identical to yours. So, you cannot rule
92. 3:06out that the body you think you're
93. 3:07sitting in is one more signal arriving
94. 3:10right on time. For most of history, this
95. 3:12stayed a thought experiment because
96. 3:14nobody could build the machine. But,
97. 3:15that is starting to change. In 2003, an
98. 3:18Oxford philosopher named Nick Bostrom
99. 3:20pointed out something simple and hard to
100. 3:23argue with. If a civilization ever gets
101. 3:24advanced enough to simulate conscious
102. 3:26minds, it won't run that simulation
103. 3:28once. It'll run it thousands of times,
104. 3:30millions. They might recreate their own
105. 3:32past to study how they got here or build
106. 3:34it simply for fun, the way we create
107. 3:36entire worlds inside video games. And
108. 3:38every one of those simulated worlds
109. 3:40would be packed with people who are
110. 3:41completely sure they're real. And it
111. 3:43wouldn't take much to fool you. A
112. 3:45simulation wouldn't have to render every
113. 3:47galaxy, just the slice you happen to be
114. 3:49looking at. The inside of an atom could
115. 3:51stay blank until someone splits one
116. 3:53open. The chair underneath you could be
117. 3:54empty until the moment you decide to
118. 3:56check. The only thing that truly has to
119. 3:58be simulated is the part doing the
120. 4:01experiencing, the mind, your mind.
121. 4:03[music] And a mind, for all its mystery,
122. 4:05might be a finite thing to compute. Your
123. 4:08brain runs on something like 100
124. 4:10trillion connections firing in patterns.
125. 4:12Enormous, but not infinite. Build a
126. 4:14machine big enough and you'd have room
127. 4:16to run not just one mind, but billions
128. 4:18of them at once. If real conscious
129. 4:20beings ever build even a handful of
130. 4:23these worlds, then simulated minds would
131. 4:25outnumber flesh and blood ones by
132. 4:27something like a billion to one. So,
133. 4:29when you ask which kind you are, the
134. 4:31math doesn't flatter you. The odds say
135. 4:33simulated. Plenty of scientists argue
136. 4:36this can't be tested at all, and they
137. 4:38may well be right. But notice that none
138. 4:40of them has managed to find the floor
139. 4:42under your feet. But here's the bigger
140. 4:44problem. You assume the people around
141. 4:46you feel things the way you do. But you
142. 4:48have never once felt anyone's experience
143. 4:50except your own. You're the one filling
144. 4:52in the rest. You watch a friend laugh
145. 4:54and you assume there's a real experience
146. 4:56happening inside them, that being them
147. 4:58actually feels like something. You can't
148. 5:00check. Philosophers describe a creature
149. 5:02called a philosophical zombie. It walks,
150. 5:05talks, flinches when it stubs its toe,
151. 5:07says all the right things at all the
152. 5:09right moments. From the outside, it's a
153. 5:11flawless human being, but inside, the
154. 5:13lights are off. Nobody home. Nothing is
155. 5:16being felt in there at all. The
156. 5:17unsettling part is that no test could
157. 5:20ever tell a zombie apart from a real
158. 5:21person, because their behavior is
159. 5:23identical. The philosopher David
160. 5:25Chalmers called this the hard problem of
161. 5:27consciousness. We can map exactly which
162. 5:30neurons fire when you see the color red.
163. 5:32We cannot explain why that firing comes
164. 5:34wrapped in an experience of redness,
165. 5:36instead of happening silently in the
166. 5:38dark, the way the rest of the universe
167. 5:39seems to. If we can't explain how a
168. 5:41brain produces experience, we can't be
169. 5:43sure that only brains can do it. Maybe a
170. 5:45powerful enough computer could, too. And
171. 5:47that is exactly the loophole a
172. 5:49simulation would need. Then there are
173. 5:51the corners of physics that a few
174. 5:52scientists point out half seriously with
175. 5:55one eyebrow raised. Reality seems to
176. 5:57have a smallest possible size, a scale
177. 5:59below which distance stops meaning
178. 6:01anything, the way an image stops making
179. 6:03sense once you zoom in past its pixels.
180. 6:06The speed of light behaves less like a
181. 6:07law and more like a hard ceiling, the
182. 6:09kind of cap you'd write into a system to
183. 6:11stop it from overloading. And a
184. 6:13physicist named James Gates says he
185. 6:16found something buried in the math that
186. 6:18looked like error correcting code, the
187. 6:20same kind of code that runs inside your
188. 6:22computer to catch its own mistakes. None
189. 6:24of this proves anything, and Gates is
190. 6:26the first to say so, but it's the sort
191. 6:28of thing that once you've heard it, you
192. 6:30can't fully unhear. So, step all the way
193. 6:32back and try to find the bottom of it.
194. 6:34Every belief you hold is propped up by
195. 6:36another belief. You trust your senses
196. 6:37because they've worked before. You
197. 6:39believe they worked before because you
198. 6:40remember it. And you lean on that memory
199. 6:42because so far it has felt reliable.
200. 6:45Each rung hangs off the one above it.
201. 6:46And when you finally climb to the top,
202. 6:48there's nothing holding the whole ladder
203. 6:50up. You either argue in a circle, or you
204. 6:52chase the justifications forever, or you
205. 6:54stop somewhere and quietly declare,
206. 6:56"This part I'll just take on faith."
207. 6:58There is no fourth option. A German
208. 7:00philosopher named Hans Albert laid this
209. 7:02trap out and named it after an old folk
210. 7:04tale about a man who tried to haul
211. 7:06himself out of a swamp by yanking on his
212. 7:08own hair. That is what proving your own
213. 7:10reality from the inside comes down to,
214. 7:13reaching up, grabbing a fistful of your
215. 7:15own hair, and pulling. So, are you real?
216. 7:18Nobody can prove that you are, not the
217. 7:20smartest philosopher who ever lived, and
218. 7:22not you either. And just as importantly,
219. 7:24nobody can prove that you aren't.
220. 7:26There's no argument and no view from
221. 7:27outside the picture that settles it in
222. 7:29either direction. The question just sits
223. 7:31there, permanently open with you stuck
224. 7:34inside it. The mathematician Martin
225. 7:35Gardner was once asked how he lived with
226. 7:37that. He said he chose to believe the
227. 7:39world is real, not because he could
228. 7:41prove it, but because that belief is
229. 7:42healthier and it works. That might be
230. 7:44the most honest answer anyone has ever
231. 7:46given. You will never get to touch
232. 7:48reality bear. You're stuck in here
233. 7:50behind your own eyes working from a
234. 7:52picture you can't fully verify, but the
235. 7:54warmth of the person beside you still
236. 7:56feels like warmth. The questions still
237. 7:58feel worth asking. And whether the
238. 7:59ground under you is solid rock or
239. 8:01running code, you're the one standing on
240. 8:03it getting to wonder about any of this
241. 8:05at all. There's exactly one thing in
242. 8:07here that no demon, no tank, and no
243. 8:09computer can take from you. It's the
244. 8:11fact that something right now is being
245. 8:12experienced at all. That part is
246. 8:14happening. Whatever this is, you're in
247. 8:16it. So, you might as well be here for
248. 8:18it.