How do you know you exist? - James Zucker

2,544,581 views ・ 2014-08-14

TED-Ed


Please double-click on the English subtitles below to play the video.

00:07
How do you know you're real?
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It's an obvious question until you try to answer it,
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but let's take it seriously.
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00:14
How do you really know you exist?
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00:17
In his "Meditations on First Philosophy,"
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René Descartes tried to answer that very question,
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demolishing all his preconceived notions and opinions
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to begin again from the foundations.
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All his knowledge had come from his sensory perceptions of the world.
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Same as you, right?
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You know you're watching this video with your eyes, hearing it with your ears.
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00:37
Your senses show you the world as it is.
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00:40
They aren't deceiving you, but sometimes they do.
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You might mistake a person far away for someone else,
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or you're sure you're about to catch a flyball,
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and it hits the ground in front of you.
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But come on, right here and now,
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you know what's right in front of you is real.
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Your eyes, your hands, your body: that's you.
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Only crazy people would deny that, and you know you're not crazy.
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01:00
Anyone who'd doubt that must be dreaming.
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01:03
Oh no, what if you're dreaming?
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01:06
Dreams feel real.
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You can believe you're swimming, flying
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01:10
or fighting off monsters with your bare hands,
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when your real body is lying in bed.
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01:15
No, no, no.
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When you're awake, you know you're awake.
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01:18
Ah! But when you aren't, you don't know you aren't,
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so you can't prove you aren't dreaming.
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Maybe the body you perceive yourself to have isn't really there.
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Maybe all of reality, even its abstract concepts,
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like time, shape, color and number are false,
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all just deceptions concocted
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by an evil genius!
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No, seriously.
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Descartes asks if you can disprove the idea that an evil genius demon
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has tricked you into believing reality is real.
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Perhaps this diabolical deceiver has duped you.
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The world, your perceptions of it, your very body.
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You can't disprove that they're all just made up,
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and how could you exist without them?
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02:01
You couldn't! So, you don't.
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Life is but a dream,
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02:05
and I bet you aren't row, row, rowing the boat merrily at all, are you?
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02:10
No, you're rowing it wearily
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02:11
like the duped, nonexistent doof you are/aren't.
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02:17
Do you find that convincing?
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02:18
Are you persuaded?
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02:20
If you aren't, good; if you are, even better,
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because by being persuaded,
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you would prove that you're a persuaded being.
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You can't be nothing if you think you're something,
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even if you think that something is nothing
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because no matter what you think, you're a thinking thing,
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or as Descartes put it, "I think, therefore I am,"
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and so are you, really.
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(Airplane engine)
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