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  • (intro music)

  • So my name's Alex Byrne.

  • I teach philosophy at MIT, and today

  • I'm going to explain an argument

  • for so-called mind-body dualism,

  • the view that we are not physical or material things.

  • And if we're not physical or material things,

  • the natural alternative is that we're

  • mental things of some kind.

  • Immaterial minds or souls,

  • as it's sometimes put.

  • Hence the term "mind-body dualism."

  • On this view, the universe contains

  • two quite different sorts of things:

  • physical bodies like stones

  • and planets and brains on the one hand,

  • and non-physical minds on the other.

  • Well why is this view important?

  • Well, physical things normally

  • aren't around forever.

  • If I smash my watch into tiny pieces

  • or throw it in a furnace, that's the end

  • of this beautiful piece of Swiss engineering.

  • The watch doesn't exist anymore.

  • Similarly if your body is devoured by worms

  • or consumed in a crematorium,

  • that's the end of this beautiful piece

  • of biological engineering.

  • Your body doesn't exist anymore.

  • So, if you're a physical thing,

  • a complicated bag of cells,

  • then your eventual bodily destruction

  • means that there's no hope for immortality.

  • So, if you're invested in the prospect

  • of life after death, a lot hangs on

  • the argument for mind-body dualism.

  • The seventeenth-century philosopher Rene Descartes

  • is the most famous proponent

  • of mind-body dualism, and that's why

  • the view is sometimes called "Cartesian dualism."

  • You'll remember Cartesian coordinates

  • from high school geometry,

  • and Descartes invented those.

  • His most famous work is called

  • "Meditations on First Philosophy,"

  • which was published in Latin in 1641.

  • And the sub-title promises that the work

  • will demonstrate the existence of God

  • and the immortality of the soul.

  • We can only do so much in a few minutes,

  • so we'll have to leave the demonstration

  • of the existence of God

  • for another episode of Wi-Phi.

  • Now the argument I'm going to present

  • is not quite Descartes's argument

  • as we find it in the Meditations.

  • It's basically a variant of Descartes's argument,

  • given by the contemporary philosopher Saul Kripke

  • in his classic book "Naming a Necessity,"

  • which was published in 1980.

  • And what's more, it's a simplified version

  • of Kripke's argument.

  • But even with the simplifications,

  • I think we can see that it certainly

  • leads to an argument that deserves

  • to be taken seriously.

  • All right, so now to the argument.

  • Let's give your physical body a name.

  • Call it "Bert."

  • Everyone, dualist or not, can agree you and Bert

  • are intimately connected.

  • Stamp on Bert's toe, and you feel pain.

  • If you decide to get some aspirin,

  • that will result in Bert moving

  • towards the medicine cabinet.

  • However, that doesn't mean that you are Bert.

  • And according to the dualist, you aren't.

  • There are two things here: you and Bert.

  • And what the dualist argument tries to establish

  • is that you are not Bert.

  • More explicitly, you are not identical to Bert.

  • You are not one in the same thing as Bert.

  • Okay, so that's the conclusion.

  • So now, to prepare for the premises of

  • the argument, we need a distinction,

  • between truths that could have been false

  • and truths that could not have been false.

  • For example, here's a truth:

  • I am a philosopher.

  • That truth could have been false.

  • I could have been a plumber, say.

  • Plumbing might have struck me as a more

  • fulfilling and secure career than philosophy,

  • and I might have studied

  • for a plumbing certificate instead

  • of studying for a PhD in philosophy.

  • Here's another example:

  • it's true that there were dinosaurs.

  • But that could have been false.

  • Evolution could have failed to produce

  • any dinosaurs, or life might not have evolved at all.

  • So some truths, then, could have been false.

  • But some truths could not have been false.

  • They had to be true, come what may.

  • For example, here's a logical truth:

  • either there were dinosaurs, or there were no dinosaurs.

  • That's true, but it didn't just happen to be true.

  • It couldn't have been otherwise.

  • However the world turned out,

  • that logical truth would have been true.

  • Here's another example, which is

  • the relevant one for our purposes.

  • Imagine that the President of the United States, say,

  • is sitting opposite us.

  • I point to him and say, "He is Barack Obama."

  • That's true.

  • But could it have been false?

  • Well, how could it?

  • How could that very man fail to be Barack Obama?

  • We have just one thing here:

  • that man, also known as "Barack Obama."

  • When I say "He is Barack Obama,"

  • I'm picking out the same thing twice over.

  • It's as if I were to say "He,"

  • pointing at Obama, "is him," pointing at Obama again.

  • A thing can't fail to be identical to itself.

  • So "He," here I point at Obama,

  • "can't fail to be identical to Obama."

  • So, when I say "He is Obama," what I say

  • is not just true, it had to be true.

  • It's one of those truths like that

  • logical truth I just mentioned.

  • It could not have been false.

  • If you're inclined to doubt this,

  • you're probably thinking of some different,

  • but related, truth that could have been false.

  • For example, it's also true that he,

  • pointing at Obama, is named "Barack Obama."

  • But that's a truth that could have been false.

  • He might have had some, different name say Fred Blogs.

  • But the truth that he is Barack Obama is not the same

  • as the truth he's named Barack Obama.

  • The first truth is not about language,

  • although of course it is stated in language,

  • like truths in general.

  • It's just about the man, Barack Obama.

  • The second truth is about language,

  • at least in part.

  • Specifically, it's about the name "Barack Obama."

  • And of course these are quite different things.

  • Barack Obama is the president, but his name

  • has not been elected to any office.

  • All right, now we're ready for the argument.

  • Go back to you and Bert, your body.

  • Imagine I point to you and say "You are Bert."

  • Suppose that's true.

  • Then, since it's just like the Obama example,

  • it's one of those truths that could not have been false.

  • In other words, if it's true that you are Bert,

  • it had to be true that you were Bert.

  • You are Bert, come what may.

  • So this gives us the first premise

  • of our argument for dualism.

  • If it's true that you are Bert,

  • then it could not have been false that you are Bert.

  • But hold on.

  • Couldn't you have existed without Bert existing?

  • For example, you can imagine being

  • disembodied, not having a body at all

  • or you can imagine that you have

  • another body, Bertha, not Bert.

  • Imagining these situations is not at all

  • like imagining, or trying to imagine, say,

  • a situation in which there's a round square table.

  • That situation seems obviously impossible,

  • not a situation that could have obtained.

  • There could not have been a round square table.

  • But there seems nothing at all impossible

  • about a situation in which you exist without Burt existing,

  • perhaps because you're disembodied,

  • perhaps because you have Bertha

  • and not Bert as your body.

  • This is not the actual situation,

  • but it seems like a possible situation.

  • You could have existed without Bert existing.

  • But if you could have existed without Bert existing,

  • then it could have been false that you are Bert.

  • A situation in which you're around and Bert isn't

  • is a situation in which you aren't Bert.

  • So this gives us our second premise,

  • "it could have been false that you are Bert."

  • So now notice that the second premise

  • is the negation of the sentence

  • after the word "then," in the first premise.

  • So our two premises have

  • the following abstract form:

  • "If P, then Q; and not Q."

  • And premises of this form logically imply,

  • by a rule of inference called "modus tollens," "not P."

  • And our two plausible seeming premises, then, imply

  • "it's not true that you are Bert."

  • In other words, you are not Bert,

  • which is the dualist conclusion.

  • Subtitles by the Amara.org community

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PHILOSOPHY - Mind: Mind-Body Dualism [HD]

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    Tracy Wang posted on 2019/04/11
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