The Philosophy of Mind I. The Cartesian View of Mind: Substance Dualism A. The Basics of Mind and Body: There are four general points that, for our purposes, characterize Descartes philosophy of mind: (1) knowledge of our own minds is more secure than our knowledge of the rest of the world. (2) our mental life is wholly private--what goes on in my mind is accessible to me alone; you can never really know about my mental events, nor I yours. (3) the mind is immaterial, made up of a completely different kind of substance ( stuff ) from the body, which is made up of matter; the essence of mind is thought, whose modes are affirmation, denial, doubt, will etc; the essence of matter is extension whose modes are having size, shape, location, parts, mobility. The view that mind and body are two completely different metaphysical substances is called substance dualism. (4) somehow, the mind and body interact: the environment impacts the senses which activates the nervous system, sending messages to the brain; somehow, out of brain activation, the immaterial mind is affected and subjective experience explodes onto the scene; moreover, different mental events in immaterial substance affect the brain, which sends impulses to the rest of the body. Since Descartes holds that mind can cause changes in the body and body can causes changes in mind, and holds that mind and body are distinct metaphysical substances, we call him a two-way interactionist substance dualist. B. Descartes Argument for dualism P-1: I can conceive that I, a thinking thing, (or my mind) can exist without the existence of my extended body. P-2: If I can conceive that my mind exists separately from my body, then it is possible that my mind can exist separately from my body. P-3: If it is possible that one thing can exist without another, then those two things cannot be identical. C: Hence, my mind cannot be identical to my body. -The argument, really, is this: since I can conceive of my mind as separate from my body, then it is possible that they are separate. But if it is possible for two things to exist separately, then they cannot be identical. C.The Problem of Mind-Body Interaction: According to Descartes, our senses, when stimulated, activate the nervous system, which sends impulses to the brain. These impulses are then gathered in the region of the brain Descartes called the common sense, which is actually what we call today the pineal gland. Each impulse in the pineal gland causes a distinct sensation in the immaterial mind, which allows the mind to gain awareness of the physical environment. But the mind can stimulate the brain in the pineal gland as well, causing effects in other parts of the body. How, though, could the material body interact with the mind which is not located in space and is not made of matter at all? That is, how could something that is located nowhere and that has no size, shape, matter or movement interact with and cause changes in something that is located somewhere and has all of these properties? Moreover, if the mind is not located anywhere, how could it interact with body at some location in the brain? D. The Problem of Individuating Minds: If two physical objects have identical physical properties--e.g. they have the same size, shape, color, weight etc.-- they are still individuated or distinct from one another since they will have different spatial locations. According to the
dualist, minds have only mental properties. But if two minds have all the same mental properties, then, unlike the case with physical objects, there d be nothing to individuate them, since minds have no spatial location. If there s nothing to individuate them, then they wouldn t be two minds. This isn t a problem of how we can tell whether there is one mind or two. Rather, the problem is that if dualism is true, then two minds that shared all the same mental properties would not be two minds--they d be one mind. And this is entirely incoherent. E. The Argument From the Law of the Conservation of Momentum The momentum of a body is its mass multiplied by its velocity. The law of the conservation of momentum states that in any system on which no external forces are acting, the total momentum of all the bodies inside the system remains constant. So if we take two colliding billiard balls as our isolated system, the sum total of the momentum of the balls before they collide is equal to the sum total of the momentum of the balls after they collide, even though the velocity of each ball is altered upon collision. Now, the Cartesian dualist claims that the mind alters the momentum of the body. But he also claims that the mind is non-physical. The problem is, if the mind is non-physical, then it has no mass, and therefore no momentum. So let s take a human mind and a human body as our isolated system. We will suppose with the dualist that the mind alters the momentum of the body. But note that if the mind itself could have no momentum, then, if the momentum of the body changes, the sum total momentum of that mind-body system must change. But this would violate the Principle of the Conservation of Momentum, which states that the total momentum of an isolated system remains constant. Since we know that this principle is true, dualism must be false. F. An epistemological problem with Cartesian Dualism: the problem of other minds 1. Zombies and Mutants: On Descartes philosophy of mind, the mind is wholly distinct from the body and one s mental life is totally private. These two characteristics combine to open up the following logical possibilities: a) The Existence of Zombies: non-conscious creatures that are physically indistinguishable from conscious beings. They have the same brain and body processes but completely lack subjective experience--they are all dark within. How could one distinguish a zombie from a conscious being? Since the Cartesian mind is non-physical, we cannot use our senses to perceive the existence of other minds: we cannot feel, see or hear minds. All we can observe are bodies. But, according to the Cartesian dualist, the mind is totally distinct from the body. No neurophysiological investigation can find conscious experience. All that we could find are beings with functioning neurophysiological systems. But zombies are beings with functioning neurophysiological systems. So there would be no way to know whether we were examining a zombie or a conscious being. For all you know, you are entirely surrounded by zombies right now. Remember, according to the Cartesian dualist, mental life is totally private: no one except myself can know what my mental life is like or even whether I have a mental life at all. Hence, the problem of zombies is a straightforward consequence of Cartesian dualism. b) Mutants: mutants, unlike zombies, are conscious beings but their consciousness is very different from ours. When they get pricked by a pin, they hear a middle C on a clarinet, yet they react by saying ouch because their brains function just like ours. Or, when they see the color that looks yellow to you, it looks blue to them. That is, everything happens in their bodies just as it does in ours, but the resultant mental events are strikingly different. 2. Reply to Zombie and Mutant Possibility: the argument from analogy: can t one just use himself as a model here and suppose that other beings have conscious life just like him? Can t
one just observe that his own mind causes affects in his own body, and conclude that the same thing happens in other bodies? But this is would be a very weak argument. All one has to go by is evidence from his own case. How could the generalization from this one case to all other beings amount to a reasonable conclusion? To say the least, his is a very weak bit of evidence for such a broad generalization. **In general, one has no more reason to believe that he is surrounded by beings whose consciousness is just like his than he does for believing that he is surrounded by zombies or mutants. We can cut open everyone s brain and see how they function but this could never tell us whether they had experiences like us or were even conscious in the first place. Believing that there are other minds out there is simply a blind article of faith. F. The Real Point of the Zombie and Mutant Possibilities: the point of these possibilities is not to force the conclusion that we ought to be skeptical about other minds. Rather it is to show the very unattractive consequences of adopting one particular philosophy of mind--descartes dualism. If we want to avoid the problem of mutants and zombies, we ought to reject Cartesian dualism and rethink our conception of mind and body. The idea is that a better conception of mind and body would not allow such bizarre and unwelcome possibilities. The reason why these are live possibilities on the Cartesian picture is because on that picture mind and body are wholly distinct entities. Hence, on an improved theory of mind, we will have to look at the mind as being more closely related to the body. III. Another Possibility: Locke, Leibniz and Occasionalism A. Locke and the Problem of Causation: John Locke thought it incredible that changes in the body can cause conscious experiences given their dissimilarity. How could the movement of a piece of steel dividing flesh cause the experience of pain when pain bears no resemblance to the movement of a piece of steel? What does dividing flesh and consequent bodily impulses have to do with the subjective feeling of pain? A conscious experience and the physical alterations which allegedly give rise to it are far too unlike one another to be bound in a causal relationship. -for Locke, a causal relationship between physical and mental events is wholly unintelligible to us. It is just a brute fact of nature that particular conscious states occur when states of the body occur--there is no natural explanation that we can discover however closely we investigate. An equally plausible explanation that can be given for why a particular conscious experience follows from a particular physical change, says Locke, is that God saw fit to annex particular modifications of consciousness to particular physical events in the body. This correlation is just a brute fact about the design of nature by God. B. Occasionalism: this is more or less the view called occasionalism: according to this view, events in the body do not cause events in the mind, but provide occasions on which God inserts mental events of appropriate kinds into our biographies. This view could be seen as a improvement upon two-way interactionist substance dualism since it avoids the difficulty of mind-body causation. The occasionalist would still be a substance dualist, since he believed there are two distinct metaphysical substances, but he would not be a two-way interactionist dualist like Descartes. C. Leibniz s Response to Locke: Leibniz subscribed to the principle of sufficient reason or the principle that there can be no fact without there being a sufficient reason why it should be so and not otherwise. According to this principle, the whole order of nature must be in principle transparent to reason; there must be a reason why things are one way and not another. If this principle is true, then it rules out Locke s theory of mind and body. For Locke, there is no reason
at all for why pain follows from a pin-prick except that God saw to it that those two events were conjoined. But this would mean, for Leibniz, that God was behaving irrationally, or acting in an unruly and unreasoned fashion --which, of course, God would never do. Rather, there must be some rational connection between the physical event and the mental event. D. Leibniz, Locke and Supervenience 1). Supervenience: For Locke, in creating the world God had to do two things: (1) create all the physical bodies and laws and (2) then annex particular mental events on to them. There is room for independent variation here: God could have created the physical world and physical laws, but annexed completely different mental events as correlates. For Leibniz, on the other hand, God merely had to do one thing: fix the physical world and its laws and from this the mental events flow. Here there is no room for independent variation: if God wanted to change something about our mental lives, he d have to change the physical world and its laws in order to do so. We express this relationship by saying that facts about minds supervene on the physical facts; that is, the physical facts and laws completely determine facts about our mental lives. So, mental facts supervene on physical facts if one couldn t change mental facts without changing physical facts. Here s a rather mundane example of a supervenience relation: the facts about the shape of an object supervene of the facts about the size and the placement of the particles that make it up. If we change the facts about the size and the placement of the particles that make the object up, then we change the facts about the object s shape. So, to fix the facts about an object s shape, God only had to do one thing: fix the facts about the size and placement of the particles that make it up. 2). Zombies, Mutants, Locke and Leibniz: For Locke, the possibility of zombies and mutants is still open. God could have fixed all of the physical facts and laws and simply decided not to annex conscious experience to some people (zombies), or to annex various experiences for the same physical changes (mutants). Hence you could have a zombie or mutant twin: you could have a twin who is physically identical to you in every last detail but who either lacks conscious experience altogether or who has different experiences annexed to different physical states. But for Leibniz, the possibility of zombie and mutant twins is ruled out. If God made an exact physical duplicate of me, that twin would have exactly the same mental life as me as well. For again, God only had to do one thing-- fix all of the physical facts and laws-- in order to write the complete mental history of the world. F. Parallelism: Blackburn s exposition of Leibniz is a little controversial. Most people regard Leibniz as a parallelist. Parallelists are substance dualists as well, but, like occasionalists, they hold that mind and body do not interact. For parallelists, mental states cause other mental states, and physical states cause other physical states, but the two substances never interact--rather, they occur in harmony with one another--they are in sync, so to speak. For example, when become aware of the change in a traffic light, this awareness is a mental state. At the same time, there is a physical state in my body, but one does not give rise to the other. My awareness causes another mental state, namely, my decision to move the car. At the same time, the physical state paralleling the moment of awareness gives rise to another physical state--the one that moves my foot on the gas to accelerate the car. So how do we explain this harmony? According to Leibniz, the harmony between mind and body is pre-established by God--like two synchronized clocks. IV. Analysis Leibniz thought there must be some rational relationship between the mental and the physical that we can make out. Facts the mind and body are so closely intertwined that to change facts
about the former you d have to change facts about the latter. The philosophical problem is to fully understand this relationship and explain why mental facts cannot vary independently of variations of physical facts. Some philosophers of the 20th century--who we will call logical behaviorists -- have used a technique called analysis to make out the relationship between the mental and the physical. A. What analysis is: attempts to spell out what makes true some mysterious kind of statement, using terms from some less mysterious class. 1. Blackburn s example: The average man has 2.4 children and 1.8 automobiles. To someone who is not very bright, this would be a mysterious statement indeed--that a man has two children and the torso of a third, and one whole car and most of another. The analysis of this statement, which would seek to eliminate the mystery, would be: Across families, the total number of children divided by the number of progenitors is 2.4, and automobiles divided by the number of owners is 1.8. We say that the first statement is analyzed or reduced to the second statement. B. The motivations for employing analysis to the philosophy of mind 1. Cartesian Introspectionist Psychology and Scientific Psychology: Descartes philosophy of mind was a metaphysical theory. On it, the mind was an immaterial substance that was not located in space, and that could not be observed or studied scientifically. Knowledge of the mind was not gained through observation and experiment but through introspection--reflecting on one s own inner, private states and describing it. The techniques and concepts employed by this brand of introspectionist psychology guaranteed that psychology would never be a science. There was no shared method for reflecting on the contents of one s own mind and no way for other psychologists to verify so called discoveries garnered through one s own introspection. At the time, then, there seemed to be an impassible gulf between the natural sciences and a study of the mind. C.Analysis and the Mind: The logical positivists, among others, wanted to mend this impassible gulf between psychology and the natural sciences and they employed the technique of analysis to this end. Recall that analysis gives an account of what makes true a statement in some problematic class using terms from some less mysterious class. Practitioners of analysis identify statements about the mind such as Jones is in pain or Mary believes it is going to rain as problematic statements to be reduced to or analyzed into other less problematic statements that spell out what is meant by the problematic statements. The key is that if psychology is to be scientific, the less problematic statements must be statements about observable phenomena that are amenable to the techniques of scientific investigation. So, if we are going to use analysis to mend the gulf between psychology and the natural sciences, we need to identify statements about observable phenomena that mean the same thing as statements about the mind. Where do we go from here? 1. Verificationism: the meaning of a statement is the conditions of its verification. That is, the meaning of a statement is the evidence gleaned from observation that would establish its truth. What evidence gleaned from observation would establish the truth of psychological statements-- for example, the statement Paul has a toothache? Well, how do we come to know that Paul as a toothache? By gathering evidence gleaned from observing Paul s behavior. -(a) a non-psychological example: Today at 1 o clock, the temperature was 72 F. What evidence would establish the truth of this? Well, among other things, that the mercury in this tube extends up to the number 72. This statement describing the evidence we call a physical test sentence. For the verificationist, the original sentence is simply an abbreviation of its physical
test sentences or the sentences which describe the conditions of its verification. Our statement about temperature can be retranslated without loss of meaning into other statements in which the word temperature no longer appears. 2. Verificationism and Statements about the Mind: According to verificationism, then, the meaning of a statement about a person s mind should be cashed out in terms of the observable phenomena that verify it--that is, in terms of the person s observable behavior. The physical test sentences for a statement making reference to a psychological state simply describe the behavioral dispositions of a person in that state. Consider the following psychological statement and its physical test sentences: (2) Paul has a toothache a) Paul weeps and makes gestures of such and such a kind. b) At the question What is the matter? Paul answers I have a toothache. c) Paul takes aspirin. d) Paul chews on one side of his mouth. d) Paul makes calls to the dentist. -These physical test sentences give the meaning of the psychological statement but no longer contain the problematic psychological term toothache. The term toothache and all other psychological terms, actually serve as abbreviations of complex descriptions of behavior. And since the test sentences use only physical terms relating to observable phenomena, psychology can finally be a part of the physical sciences. That is, statements of psychology can be translated without change of meaning, into the statements of physics. D. Logical Behaviorism and the dissolution of the Mind/Body problem 1. Zombies: if logical behaviorism is correct, then the possibility of a zombie or mutant twin makes no sense. For the logical behaviorist, all it is to be in pain is to be disposed to behave in the ways described by the physical test sentences. Hence, if your zombie twin shares all of your behavioral dispositions, then he shares your sensations. We can also put this in terms of the verification principle. If I had a zombie twin, it would be impossible to verify--there would be no observable difference between my behavior and my zombie twin s behavior. But this would mean, according to the verification principle, that the sentence I have a zombie twin is literal nonsense. The point is, the logical behaviorists used philosophical analysis to close the gap between the mental and the physical. 2. Statements about the Mind/ Body problem: for the verificationist, sentences like The soul is an immaterial substance or The mind is distinct from the body are meaningless strings of words, although they are grammatically well-formed. They are meaningless because they could not be verified by observation. Whether the mind was distinct from the body or was an immaterial substance would make no difference to the observable world. It turns out, then, that the mind-body problem is not really a problem at all--it is a pseudo-problem -- since it isn t even statable. E. The main objection to behaviorism: ignoring qualia Behaviorism ignores the inner aspect to our mental lives. For the behaviorist to be in pain is merely to be inclined to wince, cry, reach for the Advil etc. But most of us would like to object that to be in pain is to have a distinctive subjective feeling in addition to being disposed to behave in certain ways. Indeed, leaving out this subjective quality of experience--or as we say in philosophy, leaving out this quale -- is leaving out something that is absolutely essential to
being in pain. An account that spells out what it is to be in pain that does not mention the hurtfulness of pain is necessarily an incomplete account of pain. -the logical behaviorist will object that, given the verificationist principle, all it can possibly mean to be in pain is to be disposed to behave in certain ways. But we can respond by pointing out that there are other mental states with a subjective character or quale that are not associated with any discernible behavioral dispositions--such as tasting coffee. Here, the taste of coffee is part of the mental state associated with tasting coffee, much like how the hurtfulness of pain is part of the mental state of being in pain, but in the case of tasting coffee, there are no behavioral manifestations of being in such a state. Hence there are no statements about behavior into which we can analyze the experience of tasting coffee. V. Identity Theory A. Materialism: in the latter half of the 20th Century, the notion that human beings consist of the matter of which they are composed has grown to be almost universally accepted among philosophers, scientists and psychologists. Materialism is the view that the only metaphysical substance that exists is matter, or physical stuff. Hence, the materialist does not believe that the human being consists of a material body and an immaterial mind. B. The Metaphysical Identity Between Mind and Brain: The mind-brain identity theorist holds that there is a metaphysical idenity between mental states and physical states. 1. Examples of metaphysical identity: (a) temperature: the temperature of a gas is the mean molecular kinetic energy of its molecules. So God would have to do only one thing to fix a gas s temperature: fix the mean kinetic energy of the gas molecules. There is no independent variation between mean kinetic energy of gas molecules and temperature. The key is that we did not figure out this relationship through pure reason; rather, it was a scientific discovery that required experiment and observation. (b) the morning star and the evening star: we called the brightest star in the evening the evening star and the brightest star in the morning the morning star. However, we came to know later--again, through a scientific discovery--that the morning star is the evening star. They re both the planet Venus. 2. metaphysical identity and the mind: in a similar fashion to the above metaphysical identities, mind-brain identity theorists suppose that a mental state--for example, pain--is identical to a physical state of the brain--for example, the firing of C-fibers. Like the above metaphysical identities, identifying pain with C-fiber firing will be the result of a scientific discovery, gleaned through observation and experiment. The goal for identity theory, then, is to find some physical state characteristic of people sharing some mental state, and then identify the mental state with the physical state. a) Not correlation: the identity theorist is not saying that a mental events such as pain is always correlated with a physical events such as the firing of C-fibers. Rather, the identity theorist is saying that there is only one event--an event in the brain. b) Not synonymy: the identity theory, unlike logical behaviorism, is not a thesis about the meaning of psychological terms; they are not saying that pain means c-fibers are firing. c) Not causal: the identity theorist is not saying that the firing of c-fibers causes pain, but, rather, the firing of c-fibers is pain. d) numerical identity: mental and physical states are events are numerically identical--are one and the same thing. Just like the Morning Star and the Evening Star: the brightest star in the
morning and the brightest star in the evening are one and the same thing, namely, venus, but it took a scientific discovery to unearth that identity. C. Arguments for the Idenity Theory 1. The Causation Argument #1: It is commonly accepted that mental events are causes and effects of events in the body. For example, we say that Jones touching the hot surface caused him pain. But we have no idea of how this causal relationship would happen if mental events lie outside of the physical domain--if they occur in an immaterial substance. How could some physical event cause an event in something non-physical? If we accept identity theory, the problem vanishes: we would have one physical event--jones touching the hot surface--causing another physical event--the firing of C-fibers. 2. The Simplicity Argument: This argument takes off from the fact that mental phenomena correlate with some neural activity. If we do not accept identity theory, we have no explanation for why certain mental phenomena are correlated with certain neural states and not others--for example, why pain is pain correlated with the firing of C-fibers and not the firing of D-fibers. It doesn t help to say that they are correlated because the firing of C-fibers causes pain, since we could ask again: why does the firing of C-fibers cause pain instead of a tickle. These correlations or causal relationships would be brute, unexplainable facts of nature. But if we accept the identity theory, the explanation is simple: the feeling of pain occurs when C-fibers are stimulated because pain is C-fiber stimulation. D. Objections to the identity theory 1.The Multiple-Realizability of Mental States (Blackburn) What is essential to pain is the feeling of pain. If something feels like pain, then it is pain. Given this, there seems to be no reason to exclude the possibility that something that did not have C- fibers could feel pain; there even seems to be no reason to suppose that pain couldn t be felt in a non-biological system--say one made of silicon. -response: the identity theorist s response to this kind of objection is usually to recoil from type-identity theory and adopt what we call token identity-theory. That is, the identity theorist will not claim that, in general, pain is C-fiber stimulation, but will identify a particular experience of pain with a particular physical state. So my pain in my left shoulder is the stimulation of such and such fibers in my body which happen to be a c-fiber; the octopuses pain in his left tentacle is the stimulation of such and such fibers, which need not be C-fibers. 2. Semantic properties of brain states??? -Our thoughts and beliefs have meaning and can be either true or false. My belief that I am talking to you is true. But according to identity theory, that belief would be identical to some brain state. But can a brain state have meaning? Can certain neural firings be true or false? Beliefs can be misleading and thoughts can be confused. Can neural states be misleading and confused? If not, then neural states cannot be thoughts or beliefs. -response: a long time ago, it seemed equally absurd to say that sound has a wavelength or that light has a frequency or that the earth moved. What we had to do is change the way we talked and eventually these things started to make sense. So we might come to think that it isn t odd at all to say that a brain-state can have semantic properties such as meaning or truth or falsity. 3. Knowability
-My mental states are introspectively known by me as states of my conscious self. My brain states are not introspectively known by me as states of my conscious self. Therefore, my mental states cannot be my brain states. -response: this argument commits the masked man fallacy: Prozac is known as an antidepressant; fluoxetene is not knows as an anti-depressant; therefore, prozac is not fluoxetene. VI. Inverted Spectra A. The Cartesian Scenario: On the Cartesian scenario, we can imagine a world W that is an exact physical duplicate of our own @ except, for example, where we see yellow, the mutants at W see blue; likewise, where we see red, the mutants at W see green; and so on. Now, they are exact physical duplicates of us, so when Jones says That s a very yellow lemon, his mutant twin says That s a very yellow lemon, although Jones has a mental experience of yellow while his twin has an experience of blue. To put it another way, while keeping both words physically identical, God annexed blue in W to the physical states to which he annexed yellow in @. B. The Impossibility of such Scenarios 1) Light/Dark world: first, can we imagine a world that is an exact physical duplicate of ours except for the fact that where we see light, our mutant twins see dark? No. If we take a piece of gray glass and make it lighter, we see better through it. For example, we would be able to better read an eye-chart that was behind it. For our mutant twins, the glass would become darker. Does it make sense to say that they would see better through it as well? No. But if they were exact physical duplicates, then, if we were reading E A B off an eye-chart, our physical duplicates would have to as well. But they would not be able to do this in just those conditions where we would find it easiest--when the glass was made lighter. So we cannot imagine a world that is an exact physical duplicate of ours but where the inhabitants see light while we see dark. 2. Inverted Spectrum World: In an inverted spectrum world, my physically identical mutant twin would see blue where I see yellow. But, again, if he is physically identical to me, he would have to react just as I do. Now, when I look up at the sun, it is a blinding bright yellow--so bright that it would hurt my eyes and I would have to shield them with my hands. But for my mutant twin, the sun would look blue, and it seems impossible to imagine that looking at the sun would hurt his eyes as much as it would hurt mine. It therefore seems hard to imagine that he d be made to squint, or shield his eyes. This would mark a physical difference between me and my mutant twin. So it seems quite difficult to imagine a world that is an exact physical duplicate of ours but where its inhabitants have inverted spectra. 3. The Point: There is a real limit to what we can imagine about the conscious life of beings whose physical make-up is exactly like ours. We must therefore engineer a conception of mind that closes the gap between the fully functioning and responsive visual system in the brain and subjective color experience. So, contrary to Locke s assumption, conscious states are not rationally inexplicable and arbitrary add-ons with no relationship to our physical states. Siding with Leibniz, there is a rational relationship between the mind and the body that we can successfully make-out. We see yellow as bright because yellow light is closer to the frequency at which our visual systems are maximally responsive; we see blue as dark because its frequency is closer towards the point at which our visual systems do not respond at all. Our color experiences are the expressions of the physical functioning of the creatures that we are.