PHIL 2100: Introduction to Philosophy
Dr. Robert Lane
Lecture Notes: Wednesday June 23, 2010



[4.2.] Cartesian Dualism.[1]


Descartes’ Meditation VI is entitled “Of the Existence of Material Things, and of the Real Distinction Between the Soul and the Body of Man.” By the beginning of this last Meditation, Descartes thinks he can be epistemically certain of each of the following claims:



In this final Meditation, Descartes tries to prove two things:

·         physical objects actually do exist; and

·         he (a mind or soul) has a physical body, but he is not the same thing as his physical body.


The last point is Cartesian Dualism:


Cartesian Dualism (df.): the mind and the body are two totally different things, capable of existing separately.



[4.2.1.] Descartes’ Conception of the Mind.


“[M]y essence consists solely in the fact that I am a thinking thing [or a substance whose whole essence or nature is to think].” (Med VI; Sober 239)


Exactly what does Descartes mean when he says that his “essence” consists only in the fact that he is a thing that thinks? To understand that claim, we need to consider the distinction between essence and accident:


essential properties (a.k.a. essence) (df.): the properties without which a thing would not exist; if a thing x has a property F, and F is an essential property of x, then if x were to cease to have F, x would cease to exist. For example…

·         It is commonly thought that an essential property of a physical object is extension in space. If something does not take up any space whatsoever, then it is not a physical object. If this desk were to lose the property of being extended in space, it would no longer be this desk (the desk would no longer exist). [This is Descartes’ view: physical bodies are essentially extended in space.]


Descartes held that minds are essentially things that think, i.e., that a mind that loses the property of thinking is no longer a mind at all.


accidental properties (df.): a thing’s inessential properties, i.e., the traits that the thing could lose without ceasing to exist; if a thing x has a property F, and F is an accidental property of x, then if x were to cease to have F, x would not necessarily cease to exist. For example…

·         Being beige is an accidental property of this desk; if the desk were painted black, it would still be the same desk, just with a different (accidental) property.)


On Descartes’ view, every other property that he has is accidental. Any of those properties could change, and yet he would still be the same being.


Even though Descartes thinks that the mind is a completely different thing from the body, he maintains that it is very intimately related to the body:


Nature also teaches me by these sensations of pain, hunger, thirst, etc., that I am

not only lodged in my body as a pilot in a vessel. but that I am very closely united to it, and so to speak so intermingled with it that I seem to compose with it one whole. For if that were not the case, when my body is hurt, I, who am merely a thinking thing, should not feel pain, for I should perceive this wound by the understanding only, just as the sailor perceives by sight when something is damaged in his vessel; and when my body has need of drink or food, I should

clearly understand the fact without being warned of it by confused feelings of hunger and thirst: For all these sensations of hunger, thirst, pain, etc. are in truth none other than certain confused modes of thought which are produced by the union and apparent intermingling of mind and body. (Med VI; Sober 240)


In his other writings, he maintains that the pineal gland—a small organ located at the center of the brain—is the part of the body through which the mind and the body interact.[2]


Note the problem with Cartesian Dualism that Sober discusses at p.263: if the mind is non-spatial (i.e., if it is not extended in space at all), then it is completely mysterious how there can be causal relationships between the mind and the physical (spatially extended) body. This is a major problem for Cartesian Dualism, but not for the Identity Theory, as we’ll soon see.



[4.2.2.] The “Indubitable Existence” Argument


In Meditation II, Descartes presents the following argument to show that the mind and the body are two distinct things:






The “Indubitable Existence” Argument

1.      A person’s mind has the property of indubitable existence.

2.      A person’s body (including her brain) does not.

3.      Therefore, a person’s mind and body (including her brain) are not the same thing.


Descartes thought it was valid. If you are tempted to say that it is, then you are probably assuming the same principle that Descartes was assuming when he put forward this argument  (think of this as an implicit premise of the argument)…


Leibniz’s Law (a.k.a. the Principle of the Indiscernability of Identicals): (df.)

If a has some property and b does not have that property, then a ¹ b.[3]


Let’s restate the argument to make this premise explicit:


The “Indubitable Existence” Argument

1.      A person’s mind has the property of indubitable existence.

2.      A person’s body (including her brain) does not.

3.      If a has some property and b lacks that property, then a and b are not the same thing.

4.      Therefore, a person’s mind and body (including her brain) are not the same thing.


So long as (3) is included as a premise, this argument is deductively valid.



[] Sober’s Criticism.


Sober thinks there is a big problem with this argument, one having to do with the (alleged) property of “indubitable existence”: the problem is that indubitable existence isn’t really a property of things. If Sober is right, then premise 1 is false.


To understand why Sober thinks indubitable existence is not a property, we first need to recognize that some mental states are about things (beliefs that p, hopes that p, desires that p, fears that p, wishes that p… etc.) These states are called propositional attitudes: they are attitudes that one has towards propositions.


propositional attitude (df.): a psychological relationship that a person can have with a proposition (e.g., believing that, knowing that, hoping that, wishing that, desiring that, fearing that...) For example, each of the sentences

·         “Scarlett believes that tomorrow is another day.”

·         “Mike hopes that the killer will be caught.”

·         “Lois suspects that Clark is Superman.”

·         “Bill believes that the Unabomber is in prison.”

reports on a propositional attitude; in other words, each sentence says that some person has a propositional attitude. [Not all mental states are propositional attitudes; e.g., sensations and pains are not about anything… they just are.]


Doubting is a propositional attitude. You don’t just doubt; you have doubts about certain things.


Here is the root of the problem that Sober sees…


We can talk about propositional attitudes in a way that suggests that things have properties that they don’t really have.


Suppose that your best friend, Fred, is a serial killer, that you know there is a serial killer, and that you don’t know it’s Fred. You do want the police to arrest the killer, but you don’t want the police to arrest Fred.


These facts about what you believe might lead someone to think that there is a property that the person mailing anthrax has but that Fred lacks, and that therefore Fred is not the person mailing anthrax:


1.      The serial killer has the property of being the person you want arrested [i.e., you want the police to arrest the serial killer].

2.      Your friend Fred does not have the property of being the person you want arrested [i.e., you don’t want the police to arrest Fred.]

3.      If a has some property and b lacks that property, then a and b are not the same thing [Leibniz’s Law].

4.      Therefore, Fred is not the serial killer.


This seems like a sound argument if you think of being the person you want arrested as a property. But being the person you want arrested isn’t really a property of things. And neither is indubitable existence.


A more accurate way of describing the situation is this:


·         You want the following proposition to be true: “The police arrest the killer.”

·         You do not want the following proposition to be true: “The police arrest Fred.”


These are different propositions about the same person (although you don’t know that these propositions are about the same person). And it does not follow from this that Fred and the killer are different people.


Another restatement of Descartes’ argument:


1.      A person cannot doubt the following proposition: “I have a mind.”

2.      A person can doubt the following proposition: “I have a body.”

3.      Therefore, a person’s mind and his body are not the same thing.


This is not deductively valid – when we describe the situation correctly, Leibniz’s Law is no longer applicable, and the argument is invalid.


In summary, Descartes inaccurately described the situation when he said that mind had the property of indubitable existence but body does not. “Indubitable existence” isn’t a property of objects. Rather, humans doubt propositions; doubting is an attitude taken toward propositions. Descartes’ point is really about propositions, viz. that one can be doubted and another not. Nothing follows from this about the properties of mind and body.



[4.2.3.] The Arguments of Meditation VI.


Descartes puts forward the following argument that he (i.e., his mind) is not one and the same thing as his body:


… my essence consists solely in the fact that I am a thinking thing [or a substance whose whole essence or nature is to think]. And although possibly (or rather certainly, as I shall say in a moment) I possess a body with which I am very intimately conjoined, yet because, on the one side, I have a clear and distinct idea of myself inasmuch as I am only a thinking and unextended thing, and as, on the other, I possess a distinct idea of body, inasmuch as it is only an extended and unthinking thing, it is certain that this I [that is to say, my soul by which I am what I am], is entirely and absolutely distinct from my body, and can exist without it. (Med VI; Sober 239)


The following captures Descartes’ reasoning in the above-quoted passage:


The Extension Argument

1.      My mind lacks the property of extension.

2.      My body, including my brain, has the property of extension.

3.      If a has some property and b lacks that property, then a and b are not the same thing [Leibniz’s Law — implicit].

4.      Therefore, my mind is not the same thing as my body.


Later he puts forward a somewhat similar argument:


[T]here is a great difference between mind and body, inasmuch as body is by nature always

divisible, and the mind is entirely indivisible. For, as a matter of fact, when I consider the mind, that is to say, myself inasmuch as I am only a thinking thing, I cannot distinguish in myself any parts, but apprehend myself to be clearly one and entire: and although the whole mind seems to be united to the whole body, yet if a foot, or an arm, or some other part, is separated from my body, I am aware that nothing has been taken away from my mind. And the faculties of willing, feeling, conceiving, etc. cannot be properly speaking said to be its parts, for it is one and the same mind which employs itself in willing and in feeling and understanding. But it is quite otherwise with corporeal or extended objects, for there is not one of these imaginable by me which my mind cannot easily divide into parts, and which consequently I do not recognize as being divisible; this would be sufficient to teach me that the mind or soul of man is entirely different from the body, if I had not already learned it from other sources. (Med VI; Sober 243)


The following captures Descartes’ reasoning here:


The Divisibility Argument

1.      My mind is not divisible (it cannot be divided into smaller parts).

2.      My body (including my brain) is divisible (it can be divided into smaller parts).

3.      If a has some property and b lacks that property, then a and b are not the same thing [Leibniz’s Law — implicit].

4.      Therefore, my mind is not the same thing as my body.


Both arguments use the same strategy: The premises point out that, according to the ideas Descartes has about his mind and his body, they have different properties. Since they have different properties, then, by way of Leibniz’s Law, they cannot be one and the same thing. So they must be different things.


Both arguments are deductively valid—if the premises were true, then the conclusion would have to be true as well.


Sober argues that the Extension Argument and the Divisibility Argument both beg the question… no one would accept the premises unless they already accept the conclusion. Here’s why…


·         If you assume in advance that the mind and the brain are not one and the same thing, then you will be very willing to accept the first premises of Descartes’ two arguments:

  1. My mind does not have the property of extension.
  2. My mind is not divisible (it cannot be divided into smaller parts).


·         But if Descartes’ arguments are going to work, they cannot simply assume the truth of their conclusion at the outset. And if we leave open the possibility that the conclusion might be false, we cannot simply take for granted that each of the first premises is true.


·         Granted, denying the first premise of each argument, and saying that the mind has extension and is divisible sound, will sound very strange.


·         Before the molecular theory of liquids or the atomic theory was accepted, it sounded exceedingly strange to say that water was composed of very tiny particles. But this does not mean that water is not (or was not) made of tiny particles. Today, the statement that water is H2O is universally accepted and rather boring, not strange-sounding at all.


·         It is possible that the assertion that the mind has extension (takes up space) and the assertion that it is divisible are like that. They sound exceedingly weird to us, because they are such unfamiliar ideas. But that alone does not mean that they are true.


Sober concludes that the arguments of Meditations VI are inconclusive: “If the mind and the brain really are identical, then many surprising facts may follow” (262), including that the mind takes up space and is divisible.



[4.3.] Logical Behaviorism.


logical behaviorism (df.): our talk about beliefs, desires, pains, etc. is not talk about ghostly or physical inner episodes, but instead about actual and potential patterns of behavior; for example, the sentence “S wants (believes, feels) …” means that S is disposed to act in such and such a way.[4]

·         This is not so much a theory of what mental states are as much as a theory about how best to understand the vocabulary we use to talk about them, mentalistic terms like “belief,” “desire,” “feeling,” etc.


Ryle’s logical behaviorism has a negative part and a positive part.

·         The negative part: Ryle’s attack on “the myth of the ghost in the machine.”

·         The positive part: Ryle’s analysis of mentalistic vocabulary.



[4.3.1.] Negative: Ryle’s Attack on the Myth of the Ghost in the Machine.


By “the Myth of the Ghost in the Machine,” Ryle means the conjunction of these of two claims:


  1. (Cartesian) dualism: the mind and body are two distinct entities, one physical and other non-physical.
  2. mentalism: mental states are inner causes of outward behavior; beliefs, desires, etc. are inside the subject and cause behavior, which is directly observable.


Dualism is not the same thing as mentalism—they are distinct claims. Mentalism does not assume that mental states are non-physical; so far as mentalism is concerned, mental states (beliefs and so on) could be physical states of the brain. [That they are different is illustrated by the fact that the identity theory and functionalism both accept mentalism but reject dualism.]


Ryle’s Argument Against Mentalism (this is a restatement of the argument at p.266)

1.      If mental states were inner causes of behavior (i.e., if mentalism were true), then we would not have knowledge of the mental states of others (i.e., third-person skepticism would be true).

2.      But we do have knowledge of the mental states of others.

3.      Therefore, mentalism is false.


Ryle’s argument involves the problem of other minds:


the problem of other minds (df.): the problem explaining how we can know that any other human being has mental states and what those mental states are [this is an epistemological problem within the philosophy mind].


In premise 1, Ryle is assuming that if mental states are unobservable, then we cannot know anything about them. In other words, he is assuming that if mental states cannot be observed, then there is no solution to the problem of other minds.


Premise 2 basically asserts that there is a solution to the problem of other minds. If we were to reject this argument by saying that premise 2 is false, we would be committing ourselves to the view that no human being can ever know anything about another person’s mind, or even know that another person actually has a mind. It would be like saying that, for all we know, every human being other than ourselves is a zombie.

·         Philosophers of mind use “zombie” as a technical term to refer to a hypothetical human being who behaves exactly like a normal human being but who is in fact completely unconscious—it is a human who behaves normally but who lacks sentience (df.): the capacity for having conscious experiences.


Ryle’s argument is deductively valid, because it’s an instance of modus tollens. So if there’s a problem with the argument, it must be that one or both premises are false.



[] A Criticism of Ryle’s Negative Thesis.


Sober’s criticism is aimed against premise 1:

·         We have knowledge about a lot of unobservable things, and we arrive at such knowledge by way of abductive reasoning (inference to the best explanation).

·         Recall Mendel’s abductive argument for the existence of genes. From the fact that x is unobservable, it does not follow that we cannot know about x or that we cannot be justified in believing things about x.

·         So Ryle’s assumption, that if mentalism is true then third-person skepticism is true, is incorrect; the first premise of Ryle’s argument is false.


Of course, this doesn’t prove that mentalism is true; it just shows that Ryle’s argument against it is unsound.



[4.3.2.] Positive: Ryle’s Analysis of Mentalistic Vocabulary.


According to Ryle, the meaning of mentalistic terms (“believes,” “thinks,” “desires,” “wants,” “pain,” etc.) can be specified wholly in terms of behavior.


This example conveys the general idea (268):


the sentence

“S wants to drink water”

is equivalent in meaning to the sentence

“S drinks water.”


The meaning of terms (like “wants”) that seem to refer to inner states can be given by terms (like “drinks”) that refer only to behavior.


But the example is far too crude to work, since sometimes people want to drink but don’t actually do so. So “S wants to drink water” cannot mean exactly the same thing as “S drinks water.”


The way Ryle makes the analyses of mentalistic words more sophisticated is by giving the meanings of those words in terms, not of actual behavior, but in terms of dispositions to behave:

the sentence

“S wants to drink water”

is equivalent in meaning to the sentence

“S is disposed to drink water.”


Instead of analyzing mentalistic words strictly in terms of behavior, Ryle analyzes them in terms of tendencies or inclinations to behave a certain way.


This kind of analysis in terms of dispositions (a dispositional analysis) is perfectly legitimate in physics and chemistry. Consider the word “soluble”. To say that “x is soluble” is to say that “x is disposed to dissolve when placed in water.” Ryle’s point is that mentalistic vocabulary is best understood in this same dispositional way.


Another way to describe dispositions by using conditionals (if-then statements): “If S were given water, then she would drink it.” But a single conditional will not adequately capture the meaning of a mentalistic term—many conditionals are needed. For example:


“S wants to drink water” =

·         “If asked whether she wants water, S would say that she would.”

·         “If given a glass of water and a glass of lemonade, S would drink the water first.”

·         “If S were to see someone she knows walk by carrying water, S would ask for some.”

and so on...




This aspect of Ryle’s logical behaviorism reflects an assumption that was widespread among philosophers during the middle decades of the 20th century, namely, that “philosophical problems are the result of linguistic or conceptual confusion, and are to be solved (or dissolved) by careful analysis of the language in which the problem is expressed.”[5]


Notice that what Ryle is doing here is making a claim about language. It is not a claim about our minds, or about inner states, or about the connection between the brain and consciousness. Rather, it is a claim about specific words of our vocabulary: mentalistic terms like “believe,” “desire,” “feel,” etc. Ryle is an example of the attitude that long-standing philosophical problems can be solved, or “dissolved,” by paying careful attention to the meanings of our words. The idea is that, once we understand what our words really mean, the problem will turn out to be no genuine problem at all—but just a pseudo-problem.


If Ryle is right, then the traditional mind-body problem is merely a pseudo-problem.



[] Criticisms of Ryle’s Positive Thesis.


Sober offers three separate objections to Ryle’s positive thesis about the meaning of our mentalistic terms.


OBJECTION 1:  Dispositional analyses of mentalistic terms are always incomplete.


The analysis of “S wants to drink water” given above is inadequate; the following is better:


“S is disposed to drink those things that S believes are water.”


(or, as a conditional):


“If a glass of water is placed in front of S, and S believes that it is water, then S will drink it.”


Any plausible analysis of a mentalistic word will not be solely in terms of behavior, because attributing only a single mental state to an individual does not imply how that individual will behave.


A single mental state by itself (e.g., a single belief, or a single desire) is never enough to cause a given action. No one who wants to drink water will drink substance X unless he or she also believes that substance X is water. So no analysis of a word like “wants” or “believes” simply in terms of dispositions to act will ever be sufficient. Unless it includes references to other mental states, such an analysis will always omit something essential. No analysis in terms that are purely behavioristic will be complete.



OBJECTION 2: Dispositional analyses of mentalistic terms are compatible with mentalism.


Just because a property is dispositional does not mean that it does not have an inner basis that is not directly observable:

·         Consider the word “soluble.” We can give an analysis of that word that is completely in terms of how a soluble object “behaves.” But this does not imply the solubility of a substance isn’t caused by inner states of that substance. The disposition of sugar to dissolve in water stems from the internal, molecular structure of sugar.

·         Similarly, we can give a dispositional analysis of “S wants a drink of water.” But this does not imply that the disposition to drink water does not stem from inner states, e.g. inner states of the brain.


[Make sure that you understand this objection! Sober is not saying that dispositional analyses of mentalistic terms is compatible with dualism. Rather, he is saying that it is compatible with mentalism… which is simply the idea that mental states are inner, unobservable causes of outward, observable behavior.]



OBJECTION 3: Logical Behaviorism ignores qualia.


Sober explains this objection with a story told by philosopher of mind Daniel Dennett.[6]


There is an element of the mental that behavioral analyses ignore, viz. the subjective feeling of being in a specific mental state. Consider what it feels like to experience pain. This “felt” aspect of pain can exist even if it is not accompanied by any sort of behavior.


In Daniel Dennett’s story, the drug curare is given to a patient before surgery. This drug paralyzes you, but does not make you unconscious. People who are given only this drug prior to surgery report that during the surgery they experienced terrible pain. Dennett asks us to imagine just such a patient, but one who is given an amnesiac (a drug that makes you forget) immediately after the surgery is finished. That person would have no memory of anything that he or she experienced during the surgery, so he or she would not talk about the pain after he or she wakes up. In other words, he or she would exhibit no verbal pain behavior.


In this situation, there is no behavior (or disposition to behave) that could possibly be identified as the thing that the description “The person felt pain” is about. So if that person felt pain during the surgery, then that pain must be something other than behavior, or disposition to behave. Since a behavioristic analysis of the word “pain” ignores this inner, “felt” aspect of pain, it must be incomplete.


Here is how philosopher of mind Paul Churchland puts the point:


            [Logical] behaviorism … evidently ignored and even denied, the ‘inner’ aspect of our mental states. To have a pain, for example, seems to be not merely a matter of being inclined to moan, to wince, to take aspirin, and so on. Pains also have an intrinsic qualitative nature (a horrible one) that is revealed in introspection, and any theory of mind that ignores or denies such qualia is simply derelict in its duty.[7]


Churchland is using a term that has become very common and very important within the philosophy of mind over the last few decades: “qualia.”


Consider your visual experience as you stare at a bright turquoise color patch in a paint store. There is something it is like for you subjectively to undergo that experience. What it is like to undergo the experience is very different from what it is like for you to experience a dull brown color patch. This difference is a difference in what is often called “phenomenal character.” The phenomenal character of an experience is what it is like subjectively to undergo the experience. If you are told to focus your attention upon the phenomenal character of your experience, you will find that in doing so you are aware of certain qualities. These qualities—ones that are accessible to you introspectively and that together make up the phenomenal character of the experience are standardly called ‘qualia’.[8]


So the objection can be put this way: logical behaviorism completely leaves qualia—the felt, “lived” experience of our mental lives—completely out of its analysis of the mind.



Stopping point for Wednesday June 23. For next time, read Sober ch.22 (“The Mind/Brain Identity Theory”) and ch.23 (“Functionaism”).




[1] For much more information about dualism, Cartesian and otherwise, see Howard Robinson, “Dualism,” The Stanford Encyclopedia of Philosophy (Fall 2009 Edition), Edward N. Zalta (ed.), URL = <>.

[2] For more on this aspect of Descartes’ thought, see Gert-Jan Lokhorst, “Descartes and the Pineal Gland,” The Stanford Encyclopedia of Philosophy (Spring 2009 Edition), Edward N. Zalta (ed.), URL = <>.

[3] For more about this principle and others closely related to it, see Peter Forrest, “The Identity of Indiscernibles,” The Stanford Encyclopedia of Philosophy (Summer 2010 Edition), Edward N. Zalta (ed.), URL = <>.

[4] Logical behaviorism is a very different theory than methodological behaviorism. Methodological behaviorism is not a theory about the mind at all. It is instead a theory about how the science of psychology should proceed with its attempt to understand human behavior. It says that psychologists should not refer to the mind or to mental states in their theories about human behavior, but should instead limit themselves to the external, observable causes of that behavior. Since this theory does not advance a position about the mind/body problem, we will not consider it in class. Sober discusses it at length in ch.22 of your textbook.


[5] Paul Churchland, Matter and Consciousness, rev. ed., MIT Press, 1988, p.23.

[6] Dennett is one of the most prolific best known English-speaking philosophers writing today. He is a professor at Tufts University: .

[7] Churchland, p.24.


[8] Michael Tye, “Qualia,” The Stanford Encyclopedia of Philosophy (Summer 2009 Edition), Edward N. Zalta (ed.), URL = <>.

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