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DualismDualism

March 28 2007March 28 2007

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DualismDualism

We’ll end with Descartes’ We’ll end with Descartes’ argument for what may be his argument for what may be his most famous conclusionmost famous conclusion

According to Descartes we don’t According to Descartes we don’t think by having bodies arranged think by having bodies arranged in a clever way (like a fancy in a clever way (like a fancy computer)computer)

Rather minds are separate thingsRather minds are separate things

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DualismDualism

The view that minds and brains are The view that minds and brains are two kinds of things is called two kinds of things is called dualismdualism

The view that there is only one kind The view that there is only one kind of substance is called of substance is called monismmonism

The most common kind of The most common kind of monistmonist view is view is materialismmaterialism, the view that , the view that there are only material entitiesthere are only material entities

A monist who only believed in A monist who only believed in mental entities is an mental entities is an idealistidealist

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DualismDualism

The argument Descartes makes The argument Descartes makes at the start of the Meditation is at the start of the Meditation is made slightly more explicit at on made slightly more explicit at on page 54page 54

Descartes relies on the Descartes relies on the possibilitypossibility of our existing without our bodiesof our existing without our bodies

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DualismDualism

1.1. It is possible that my mind and It is possible that my mind and my body could be separatedmy body could be separated

2.2. If it is possible that my mind and If it is possible that my mind and my body could be separated, my body could be separated, then they are distinct entitiesthen they are distinct entities

3.3. So my mind and my body are So my mind and my body are not identicalnot identical

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Dualism and PossibilityDualism and Possibility

Premise 2 is very oddPremise 2 is very odd It looks like Descartes is arguing It looks like Descartes is arguing

something of the form:something of the form:pp is possibly true, so it is actually is possibly true, so it is actually truetrue

He is arguing from the possibility He is arguing from the possibility of minds and brains being not of minds and brains being not identical to their being actually identical to their being actually not identicalnot identical

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Dualism and PossibilityDualism and Possibility

This looks like a bad ideaThis looks like a bad idea Consider the following argumentConsider the following argument

1.1. It is logically possible that Cornell It is logically possible that Cornell will win the NCAA basketball will win the NCAA basketball championship next yearchampionship next year

2.2. So, Cornell will win the NCAA So, Cornell will win the NCAA basketball championship next yearbasketball championship next year

Don’t take that argument to Vegas!Don’t take that argument to Vegas!

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Dualism and PossibilityDualism and Possibility

But actually this premise is correctBut actually this premise is correct This is because of special This is because of special

properties of claims about identityproperties of claims about identity If If aa and and bb are identical, they have are identical, they have

all of the same propertiesall of the same properties Really, it’s improper to use ‘they’ Really, it’s improper to use ‘they’

there because they are one thingthere because they are one thing

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Dualism and PossibilityDualism and Possibility

Here is a property Here is a property aa has: has:Necessarily being where Necessarily being where aa is is

Since Since bb is is aa, that’s also a property , that’s also a property of of bb

So if So if aa and and bb are identical, are identical, bb has has the property:the property:Necessarily being where Necessarily being where aa is is

That is, That is, aa and and bb must be in the must be in the same placesame place

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Dualism and PossibilityDualism and Possibility

If my mind and my brain were If my mind and my brain were identical, then they would by identical, then they would by necessity be co-locatednecessity be co-located

If they aren’t necessarily co-If they aren’t necessarily co-located, i.e. if God can separate located, i.e. if God can separate them, then they are not identicalthem, then they are not identical

And that’s Descartes’s second And that’s Descartes’s second premisepremise

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Dualism and PossibilityDualism and Possibility

Descartes also has an argument for Descartes also has an argument for the first premisethe first premise

1.1. If I can conceive of something If I can conceive of something without contradiction, then that without contradiction, then that thing is at least metaphysically thing is at least metaphysically possible. possible.

2.2. I can clearly conceive of a world in I can clearly conceive of a world in which I exist but my body does not. which I exist but my body does not.

3.3. So it must be possible for me to So it must be possible for me to exist without my body. exist without my body.

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Dualism and PossibilityDualism and Possibility

Arnauld argues that when we don’t Arnauld argues that when we don’t understand something we conceive its understand something we conceive its possibility even though it’s impossiblepossibility even though it’s impossible

See pages 107-112 of CottinghamSee pages 107-112 of Cottingham So perhaps this argument is too strongSo perhaps this argument is too strong We’ll come back to similar arguments We’ll come back to similar arguments

when we look at David Chalmers’ when we look at David Chalmers’ argument for a version of dualismargument for a version of dualism

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Dualism and PossibilityDualism and Possibility

But Descartes could get by But Descartes could get by without this strong claim, for without this strong claim, for there are other differences there are other differences between mind and bodybetween mind and body

1.1. My body changes while my mind My body changes while my mind stays the samestays the same

2.2. My mind changes while my mind My mind changes while my mind stays the samestays the same

1 is possible, 2 is impossible1 is possible, 2 is impossible

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Dualism and PossibilityDualism and Possibility

We don’t need to imagine mind being We don’t need to imagine mind being split from body to see 1 is possiblesplit from body to see 1 is possible

Just consider what happens when my Just consider what happens when my body digests food while I’m asleepbody digests food while I’m asleep

My body changes, my mind does notMy body changes, my mind does not More fantastically, imagine replacing a More fantastically, imagine replacing a

neuron with a chip that plays the neuron with a chip that plays the same rolesame role

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ResponsesResponses

We’ll end with three responses We’ll end with three responses that could be made to this that could be made to this Cartesian argumentCartesian argument

First, we will question the logical First, we will question the logical principle involvedprinciple involved

Second and third, we’ll look at Second and third, we’ll look at two ways in which this may not two ways in which this may not lead to any form of lead to any form of dualismdualism

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Leibniz’s LawLeibniz’s Law

The logical principle that Descartes is The logical principle that Descartes is using is often called Leibniz’s Lawusing is often called Leibniz’s Law

Many people think that Leibniz’s Law Many people think that Leibniz’s Law needs to be qualified in certain casesneeds to be qualified in certain cases

1.1. Lois Lane believes Superman can flyLois Lane believes Superman can fly

2.2. Lois Lane does not believe Clark Kent Lois Lane does not believe Clark Kent can flycan fly

But still Superman is Clark Kent!But still Superman is Clark Kent!

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Leibniz’s LawLeibniz’s Law

You might infer that the law You might infer that the law doesn’t hold when we’re talking doesn’t hold when we’re talking about beliefsabout beliefs

And once you’ve allowed in a And once you’ve allowed in a qualification to the law, you qualification to the law, you might wonder whether other might wonder whether other qualifications come inqualifications come in

But this is not much of a positive But this is not much of a positive response to Descartesresponse to Descartes

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ConstitutionConstitution

Two more responses will look at ways Two more responses will look at ways in which Descartes’s argument might in which Descartes’s argument might be be soundsound, but not entail dualism, but not entail dualism

The body might The body might constituteconstitute the mind the mind The mind might be a The mind might be a propertyproperty of the of the

bodybody In neither case is the mind In neither case is the mind identicalidentical

to be body, but nor is dualism trueto be body, but nor is dualism true

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ConstitutionConstitution

Consider the relationship between Consider the relationship between an orchestra, say the New York an orchestra, say the New York Philharmonic (NYP), and its Philharmonic (NYP), and its membersmembers

The NYP is not identical to its The NYP is not identical to its membersmembers

It is over 170 years old, and none It is over 170 years old, and none of its members are that oldof its members are that old

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ConstitutionConstitution

So is there some So is there some thingthing, the , the orchestra, over and above the orchestra, over and above the members, and wholly distinct members, and wholly distinct from themfrom them

No; the members No; the members constituteconstitute the the orchestraorchestra

In previous times, different In previous times, different members constituted the members constituted the orchestraorchestra

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ConstitutionConstitution

We might say the same thing We might say the same thing about the body/mind relation as about the body/mind relation as the players/orchestra relationthe players/orchestra relation

The body constitutes the mindThe body constitutes the mind The mind might have been The mind might have been

differently constituteddifferently constituted It is not some It is not some extraextra thing in the thing in the

worldworld It is not It is not distinctdistinct from the body from the body

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ConstitutionConstitution

Note that we can conceive of the Note that we can conceive of the orchestra being non-physicalorchestra being non-physical

I think that’s probably possibleI think that’s probably possible Maybe we’d call it the NY AngelicMaybe we’d call it the NY Angelic A physical thing could have been A physical thing could have been

constituted by non-physical stuffconstituted by non-physical stuff Minds might have been non-Minds might have been non-

physical, but actually are physicalphysical, but actually are physical

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PropertiesProperties

Here is a variant of Descartes’ Here is a variant of Descartes’ argument for dualismargument for dualism

1.1. My body changes without my My body changes without my weight changingweight changing

2.2. My weight changes without my My weight changes without my weight changingweight changing

Since 1 is possible and 2 is Since 1 is possible and 2 is impossible, my body is not impossible, my body is not identical to my weightidentical to my weight

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PropertiesProperties

Should we conclude there is some Should we conclude there is some extra thing in the world, my extra thing in the world, my weight, that is wholly distinct from weight, that is wholly distinct from my body?my body?

That would be absurdThat would be absurd My weight isn’t any kind of thing My weight isn’t any kind of thing

at all, so it isn’t a distinct thingat all, so it isn’t a distinct thing Rather, it is a Rather, it is a propertyproperty of my of my

bodybody

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PropertiesProperties

Descartes’ argument for dualism Descartes’ argument for dualism leaves open the possibility that leaves open the possibility that my mind is a property of my bodymy mind is a property of my body

Gilbert Ryle, who’ll we start on Gilbert Ryle, who’ll we start on next time, thinks that is the right next time, thinks that is the right response to makeresponse to make