PHI 1500: Major Issues in Philosophy Session 16 November 3 rd, 2014 Philosophy of Mind: Descartes 1
Philosophy of Mind OGen concerned with explaining the relakonship between our minds and our physical bodies, Or more generally, the metaphysical relakonship between minds and the physical world. Many philosophers, like Descartes, have offered disknckve solukons to the mind- body problem: the problem of specifying the relakonship between mind and body. SoluKons to the mind- body problem generally divide into: Dualist views, which treat the mind & body as different enkkes vs. Monist views, which say that mind & body are really the same thing Dualism monism 2
Our old friend Descartes (1596-1960) defended an influenkal dualist view of the mind. Philosophers call his view Cartesian dualism, to disknguish it from other versions of dualism, which make different claims about how the mind & body relate to each other. To understand his view, some metaphysical terms will be helpful: A substance is a type of stuff. Everything that exists is made out of some kind of substance. E.g., water, steel, and bone are physical substances. Some people think that thoughts, feelings, and dreams must be made out of a sort of mental substance. Substances have proper7es, i.e., qualikes by which a substance can be described. E.g.: green, fluffy, quick, liquid, warm 3
Types of Dualism Mind stuff One type of stuff Body stuff Cartesian dualism is a type of substance dualism: It says that minds & bodies are two dis7nct types of substances Minds are res cogitans: things that think (believe, imagine, feel emokons, etc.) Bodies are res extensa: things that are extended in space. Contrast this with property dualism, in which minds & bodies are one substance, which has two dis7nct types of proper7es: mental ones, and physical ones. We will read a defense of property dualism by Frank Jackson next week. Mental properkes Physical properkes 4
In MeditaKon II, Descartes claimed he could imagine himself without a body, and concluded that he must be an immaterial thinking thing, not his body. He realizes, in MeditaKon VI, that he does not have evidence to conclude decisively that his body really exists. He will build off of the convickon that he is an immaterial thinking thing, in order to demonstrate that: His body really does exist His body has very different properkes from his mind Thus, his body and mind are made of different substances. 5
Existence of the Body AGer doubkng everything he has ever believed, Descartes cannot - see that, from this disknct idea of bodily nature that I find in my imaginakon, any argument can be derived that will lead necessarily to the conclusion that some body exists. (52) All of the evidence for his having a body, e.g.: Feeling hunger, thirst, and other such appektes, Feeling emokons with a bodily sensakon, like joy, sadness, and anger; Sensing the qualikes of other physical things, Experiencing pleasure and pain from interackng with other physical things came from his senses, which he no longer trusts. 6
Since starkng the MeditaKons, Descartes does not trust sensory evidence for the existence of his body. many experiences gradually undermined all the faith I had placed in the senses. (54) He concludes: in maeers of the external senses our judgments are at fault. (54) Even sensakons arising from our own bodies can be misleading! I had ogen heard from people whose arm or leg had been amputated, that they skll occasionally seemed to feel pain in the part of the body they were missing, (ibid.) So maybe he should doubt that his bodily sensakons correspond to real physical events. phantom limb pain 7
But, Descartes says that although I do not think that all that the senses seem to teach me is to be rashly accepted, I do not think that it should all be called into doubt. (55) Descartes arguments that: a) bodily things exist, Remember (from MeditaKons I & II) that Descartes is sure that he cannot doubt that: God exists, God is omnipotent, God is perfect and good, God could not deceive him. b) minds and bodies are disknct types of substances, both rest upon several assumpkons about God. 8
Argument for the Existence of the Body Descartes says that God has endowed [him] with a strong propensity to believe that he has a physical body and is affected by bodily things (56). And if it turned out that bodily things did not really exist (in some sort of substance), it would be impossible to think of [God] except as a deceiver. (ibid.) Descartes argument: 1. If bodily things did not exist, then God must have deceived him into firmly believing that bodily things do exist. 2. God is no deceiver. 3. And therefore bodily things exist. (ibid.) What argument form is this? 9
Argument for Dualism since I know that whatever I clearly and disknctly understand can be produced by God such as I understand it to be, (because, if God is omnipotent and omniscient, he can make anything we can think of) In other words, Whatever I can clearly and disknctly understand something, God can make. then if I can clearly and disknctly understand one thing without another, this is sufficient for me to be certain that the one is disknct from the other, since they can at least be produced separately by God. (55) If I can clearly and disknctly understand one thing without another, then God can make those things disknct from one another. 10
Argument for SeparaKon of Mind & Body Next, from the very fact that I know I exist, (From MeditaKon II: if he can be deceived, he must exist). I rightly conclude that my essence consists in this alone, that I am a thinking thing. (55)... I have a body, which is very closely conjoined to me, yet because, one the one hand, I have a clear and disknct idea of myself, insofar as I am a thinking and not an extended thing, and on the other, a disknct idea of the body, insofar as it is only an extended and not a thinking thing, it is certain that I am really disknct from my body and can exist without it. (55) In other words, I can clearly and disknctly understand myself without my body. 11
Argument for SeparaKon of Mind & Body 1. If I can clearly and disknctly understand something, then God can make it so. 2. If I can clearly and disknctly understand one thing without another, then God can make those things disknct from one another. 3. I can clearly and disknctly understand myself without my body. 4. Therefore God made minds separate from bodies. 12
Leibniz s Law Descartes argument for dualism rests upon the following principle (later described by the German philosopher G.W. Leibniz): If thing A and thing B have all the same proper7es, including their posikon in space, they are indiscernible from one another you can t tell them apart. If A and B are indiscernible, they are iden7cal: A = B. E.g., water & H 2 O are idenkcal. But if A and B have different proper7es, even if they take up the same posikon in space, we could tell them apart (they are discernible, or disknguishable, from one another). If A and B are discernible, they must not be idenkcal: A B. E.g., water & the sugar dissolved in it are not idenkcal. 13
Descartes Use of Leibniz Law Descartes calls aeenkon to many differences in proper7es between his mind (i.e. his self) and his body: The mind enables thinking, but the body cannot. The body is extended in space, but the mind is not. We are in control of our thoughts, but not our bodily sensakons. We can be deceived about our bodily sensakons, but not about our thoughts. The body can be divided into parts, but the mind cannot. The mind is part of his essence, but his body is not. 14
Descartes Use of Leibniz Law Thus, he assumes as a premise that: Minds & bodies have different properkes. By Leibniz s law, if two things have different properkes, they cannot be idenkcal. Hence, minds & bodies must not be idenkcal. Also, assuming that if two things are not idenkcal, they cannot be the same substance, Descartes will reason that: Minds & bodies are different substances. 15
Argument for Substance Dualism Descartes says that if he is merely a thinking thing, he can imagine himself without imaginakon and sensakon, or his ability to move through space. Therefore, he can exist without his body. But he has already argued that bodily things do exist Descartes reasons that if indeed these exist, they must inhere in a bodily or extended substance, (assuming that everything that exists in the world has some sort of substankal basis) but not, however, an intelligent one; For the clear and disknct concept of [sensakons & movement] includes some measure of extension, but does not at all include intelleckon [i.e., thinking, or cognikon]. (56) 16
Argument for Substance Dualism So, Descartes has argued that: minds exist bodies exist Anything that exists has a substance. Things with different properkes are made of different substances. Descartes thinks: I am made of mind substance (res cogitans), And bodies are made of physical substance (res extensa) Minds & bodies are different substances. 17
Argument for Dualism 1. Bodily things exist. 2. Whatever I can clearly and disknctly understand something, God can make. 3. If I can clearly and disknctly understand one thing without another, then God can make those things disknct from one another. 4. Minds & bodies have different properkes. 5. Therefore I can clearly and disknctly understand myself without my body. 6. Therefore God made minds separate from bodies. 7. Therefore, minds & bodies are different substances. 18
CriKque of Descartes Use of Leibniz Law Mind stuff Body stuff Descartes argued that the mind & body must be disknct substances because minds & bodies have dis7nct proper7es, and thus we can understand them apart from each other. But the properkes that Descartes uses to tell them apart are not clearly intrinsic proper7es, belonging to the mind and body themselves. Rather, they are rela7onal proper7es: i.e., facts about how Descartes can think about those things, and whether or not he can doubt their existence. Video on the Masked Man Fallacy 19
One challenge for substance dualists is to explain how the mind & body can interact with one another, if the body is extended in space, but the mind is not. Descartes thought that the interackon took place in the pineal gland in the center of the brain. He thought this must be where the soul exists, because it is right in the center of the brain. On Descartes view, all human behavior can be explained mechanis<cally, as a circuit of causes & effects from the mind to the body. E.g., mental events (like the thought, point at the arrow! ) cause changes in the physical body (muscle contrackons that move the arm to point at the arrow) 20
So for Descartes, minds are ghostlike, and bodies are machine- like. But trouble skll remains: how can an immaterial thought cause our material body to move in a certain way? Or how can an event in our physical body (like ingeskng a hallucinogenic drug) cause mental experiences? CriKcs of substance dualism think Descartes has not given an adequate explanakon of how these interackons occur. We will discuss a famous crikque of Cartesian dualism by Gilbert Ryle for next class. 21