Dualism and the Mind/Body Problem


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In the philosophy of mind, one of the most contested topics is that of the mind/body problem. This concept has to do with the relationship between the mental and the physical. When I say the word physical, I am talking about things that can be explained using our senses, for example a chair. I can describe the way a chair looks, its color and shape, when I see it. I can describe the way it sounds when I sit on it, and the way it feels when I touch it. I could go on to describe its smell and taste as well. I could use my senses to describe a table, a ball, an orange, a flower, and nearly all other physical objects, but it would sound very weird if I were to try and apply them to mental objects. A mental object can be anything from the mind and beliefs and desires, to emotions and sensations. If I were to say “This desire feels soft” or “My mind smells like peaches” you would think I was making no sense. It is clear that we have a mind that contains our beliefs, desires, sensations, and emotions. It is also clear that we have a brain; a physical thing made of tissue containing billions of neurons. These differing definitions pose the question of whether the mind and the brain are the same thing, or whether they are two different objects, and perhaps the mind is not physical at all.[footnoteRef:2] [2: Sober, Elliott. (2013). Core Questions In Philosophy. New Jersey: Pearson, p. 204. ]

Though many different arguments have been presented that claim to give an answer to this problem, the solution that I will be focusing on in this paper is the idea of dualism, proposed by René Descartes. Descartes’s provides two arguments to support his notion that the mind is a nonphysical object that is distinct from the whole body and all of its physical parts.[footnoteRef:3] Though Descartes’s arguments appear to offer a valid reason for believing that the mind and the body are two separate entities, I will argue that the criticisms posed by Elliott Sober thoroughly invalidate Descartes’s explanation.[footnoteRef:4] [3: Ibid.] [4: Ibid. ]

I will begin by discussing dualism in general and how it differentiates from other solutions to the mind/body problem (II). I will then briefly discuss a principle known as Leibniz’s Law, which Descartes utilizes in both of his arguments, to better explain how they are structurally valid (III). Subsequently, I will present Descartes’s two arguments for dualism (IV) and will follow with Sober’s criticisms of these arguments (V). I will go on to present my own evaluation of why I believe Sober clearly invalidates Descartes’s way of reasoning (VI). Lastly, I will reiterate the main points of this paper to further emphasis my thesis (VII).

How Dualism Differentiates From Other Solutions to the Mind/Body Problem.

In general, Descartes’s dualism is the idea that there are two kinds of things in the world: physical objects and mental objects (like minds, pains, and beliefs).[footnoteRef:5] According to dualism, the brain and the body which it inhabits are physical things, while the mind, which is a nonphysical thing, is distinct from the brain and body.[footnoteRef:6] For example, a dualist would believe that the sensation of being in pain is a completely different phenomenon from a neuron firing in your central nervous system. The opposing view to this is the Mind/Brain Identity Theory, which claims that your mind and brain are one and the same object and that the mental properties you have are actually physical properties.[footnoteRef:7] So, take the same example from before, someone who believes the Mind/Brain Identity Theory would claim that to be in pain is the exact same thing as the physical event of having a neuron fire in your central nervous system.[footnoteRef:8] In the following sections I will delve deeper into the topic of Cartesian Dualism and will begin by explaining Leibniz’s Law which better illustrates the argument Descartes attempts to make. [5: Ibid.] [6: Ibid.] [7: Ibid. ] [8: Ibid. ]

Leibniz’s Law

Descartes utilizes a certain principle in both of his arguments for dualism, called Leibniz’s Law. These arguments attempt to defend dualism by finding a property that the mind has but the body lacks.[footnoteRef:9] Though I do not believe his arguments are valid, the principle of Leibniz’s Law is perfectly reasonable. It is based off the idea that if and are identical, then they must have exactly the same properties. So, if you can find at least one property that has and lacks, then you have shown that and b are distinct entities.[footnoteRef:10] For example, if two identical twins were trying to pass themselves off as one in the same, and yet one of them had a freckle that the other did not, through Leibniz’s Law you would know that these two people were really separate beings. You would have found a characteristic that one sibling possess and the other does not. In the case of the mind/body problem, if Descartes can prove that the body has at least one property that the mind does not, he will have proven that they are in fact two separate objects. In the next section, you will see how exactly Descartes puts this principle to use in his arguments. [9: Ibid., 205] [10: Ibid. ]

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Descartes’s Arguments

  1. The Indubitable Existence Argument

In the Indubitable Existence Argument, Descartes uses the idea of doubt to prove his theory of dualism. He claims that you cannot doubt that you have a mind, but you can doubt that you have a body.[footnoteRef:11] Descartes supported the first half of this premise by saying that if you attempt to doubt that you have a mind, you will find yourself entertaining a thought, and so you must grant that you have a mind after all.[footnoteRef:12] On the other hand, he believed that it was possible for you to deny that you had a body, for example, you could be a spiritual being or any other sort of intangible soul. Descartes’s argument would take a form similar to this: [11: Ibid. 206] [12: Ibid. ]

Premise 1: I can doubt that I have a body.

Premise 2: I cannot doubt that I have a mind.

Therefore, the mind and the body are two different objects.[footnoteRef:13] [13: Ibid. ]

Dualism would in turn follow from the premises according to Leibniz’s Law, because Descartes has shown a property that the body has and the mind does not. For arguments sake, Sober grants that Descartes’s premises in this argument are valid, and instead questions whether dualism validly follows from the premises.[footnoteRef:14] [14: Ibid. ]

Though I will not go into Sober’s criticism quite yet, it is important to understand what property Descartes is claiming that the mind has with this argument. Descartes claims that his mind has the property of indubitable existence, and that his body lacks this property.[footnoteRef:15] For an object to have the property of indubitable existence that means that the possessor of this object cannot doubt that the object exists. Note, that this must all be in the first-person case because though it is not possible for me to doubt that I have a mind, I could very easily doubt that anyone else has one. [15: Ibid.]

  1. The Divisibility Argument

Descartes’s second attempt at proving dualism is through the Divisibility Argument. This argument makes the claim that physical things have spatial parts and extension, and the mind does not. The argument would take the following form:

Premise 1: My body has the properties of divisibility and extension.

Premise 2: My mind does not have the properties of divisibility and extension.

Therefore, my mind and my body are two different objects.[footnoteRef:16] [16: Ibid. ]

For example, the brain has spatial parts because a surgeon could divide my brain into several pieces, if he chose to do so.[footnoteRef:17] My mind, on the other hand, could not be divided into pieces by any manner. The brain also has the property of extension because it takes up physical space and has spacial location.[footnoteRef:18] We know this because we can physically see the grey matter that is our brain and we know that it is located in our skulls. Conversely, it would sound very weird to say, “My mind is located between my ears” or “My mind ways five pounds”. According to Leibniz’s Law, dualism would also follow from this argument. [17: Ibid. 210] [18: Ibid. ]

Sober’s Criticisms

  1. The Superman Counterexample

With regards to the Indubitable Existence Argument, Sober offers an analogy that proves how the property of indubitable existence is not genuine. He illustrates this through the example of Lois Lane wanting to marry Superman. Of course, Lois Lane does not know that superman is in fact Clark Kent, so if someone were to ask her is she wanted to marry Clark Kent she would say no. So, does it follow from this, using Leibniz’s Law, that Superman and Clark Kent are two different people?[footnoteRef:19] Obviously not. The following argument would not be valid: [19: Ibid. 207]

Premise 1: Lois Lane wants to marry Superman.

Premise 2: Lois Lane does not want to marry Clark Kent.

Therefore, Superman is not identical with Clark Kent.

Sober provides this analogy to show how the Indubitable Existence Argument misinterprets how Leibniz’s Law is meant to be applied. Leibniz’s Law, when properly understood, does not license the conclusion of nonidentity.[footnoteRef:20] The premises of this argument may be true, but it does not mean that the conclusion follows from them. Now, where does this leave us with the mind and body? [20: Ibid.]

The reason that Sober believes an object cannot have the property of indubitable existence is because the ability to doubt is something that we either do or fail to do to propositions. The ability for me to doubt whether or not I have brown hair, in no way changes the fact that I do have brown hair. The same goes for my ability to doubt that I have a brain or my inability to doubt that I have a mind. The premise, “I can doubt that I have a body”, does not tell me any property of the body. The same way that the premise, “ I cannot doubt that I have a mind”, does not tell me any property of the mind. These propositions merely tell me about my beliefs and my ability to believe certain things. It is for this reason that Descartes has unsuccessfully attempted to show that the body has a distinct property from the mind in this argument.

  1. Criticism of the Divisibility Argument

Unlike the previous argument, the Divisibility Argument is valid, however, Sober claims that it begs the question.[footnoteRef:21] Descartes’s premises for this argument make the claim that the mind does not have spatial parts or extension. Now, as I mentioned before, Sober concedes that assigning properties of the brain to the mind sounds very odd. For example, the idea that the mind is made of tissue and has veins and blood coursing through it, or saying that the mind can be located within out skulls, seems very strange. However, is this enough to say that this premise is not true all together? Sober believes not. [21: Ibid. 210]

Sober offers the example of H2O and water. Before the atomic theory came to be, the idea that water was made of tiny little particles would have sounded bizarre to many people as well.[footnoteRef:22] Nonetheless, this does not make the statement any less true. It is for this reason that Sober claims the divisibility argument is inconclusive. We cannot yet know all that science will discover, and it is possible that in the future the idea of the mind and brain being one will not sound peculiar to us at all. [22: Ibid.]


I will begin by explaining why Sober’s criticism of the first argument holds true. The example of Lois Lane shows exactly how Descartes is, in essence, attempting to use the idea of indubitable existence to formulate some distinction between the mind and the body, when this property cannot be applied to objects like these. Doubting and desiring are merely attitudes that we can have towards a proposition.[footnoteRef:23] These attitudes in no way describe or change the objects that the propositions are about. What Sober says can be learned from the Lois Lane analogy is this: Even if one proposition is desired whereas another is not, it does not follow that what the first proposition is about differs from what the second proposition is about.[footnoteRef:24] To give you an illustration separate from that of Lois Lane, take for example a young child who does not know that H2O means the same thing as water. If the child were to say “I want water” and yet say no to being offered H2O, it would not mean they were two different things. It would only mean that his propositional attitude towards these objects was different. I believe Sober clearly invalidates this argument by showing Descartes’s method does not work when talking about things such as the mind and body. [23: Ibid. 207] [24: Ibid. ]

The criticism that Sober presents for Descartes’s second argument is not as straightforward, but I do believe it shows there is a flaw in this argument as well. Descartes is expecting people to believe that dualism can proved from the premises that (1) the body has the properties of divisibility and extension and (2) the mind does not have the properties of divisibility and extension. Sober believes that to accept the premise you must already believe that dualism is true.[footnoteRef:25] If you don’t already believe that dualism is true, you have no reason to believe that the mind does not have divisibility and extension. For example, a mind/body identity theorist would say that the mind does have these properties because it is the same thing as the brain. So this argument would do nothing to convince them otherwise. Due to the fact that this argument is circular and cannot thoroughly prove what science will or will not discover, I see no reason to take this as evidence for dualism. [25: Ibid. 210]


Ultimately, Descartes’s efforts to provide us with a reasoning to accept dualism as true falls utterly short. Sober provided sufficient evidence that works to invalidate both of these arguments, leaving Descartes with no remaining explanation for dualism. Sober does not, however, say that dualism is false, he merely asserts that Descartes’s two arguments were unsuccessful.

Last Updated on October 17, 2020 by EssayPro