Philosophy of Mind

Course No. 424 CUR' E GUIDEBOOK The Philosophy of Mind Lecture 1: Dualism-Descartes' Legacy Lecture 2: Alternatives to Dualism-Materialism and Its Discontents Lecture 3: Strong Artificial Intelligence Lecture 4: The Chinese Room Argument and Its Critics Lecture 5: Can a Machine Think? Lecture 6: Is the Brain a Digital Computer? Lecture 7: Some Solutions to Descartes' Problems Lecture 8: The Structure of Consciousness Lecture 9: How to Study Consciousness Scientifically Lecture 10: How the Mind Works-An Introduction to Intentionality Lecture 11: The Structure of Action and Perception Lecture 12: The Construction of Social Reality 1-800-TEACH-12 1-800-832-2412 THE TEACHING COMPANY`' 4151 Lafayette Center Drive, Suite 100 Chantilly, VA 20151-1232 www.teachl2.com Grea Coats Teaching hat engages the mind The Philosophy of Mind Professor John R. Searle University of California at Berkeley John R. Searle, D. Phil. University of California, Berkeley John R. Searle is one of America's leading philosophers. He is the Mills Professor of Philosophy at the University of California, Berkeley, where he has been a member of the faculty since 1959. He attended the University of Wisconsin, where he was awarded a Rhodes Scholarship to Oxford in his junior year. He received his B.A. (1955), M.A., and D. Phil. (1959) degrees from Oxford. He was a lecturer in Oxford from 1956 to 1959, prior to accepting his appointment in Berkeley; and he has held visiting professorships in the United States, England, Canada, Norway, Germany, Italy, France, and Brazil. Professor Searle's books include Speech Acts, Expression and Meaning, Intentionality, Minds, Brains and Science, The Rediscovery of the Mind, and The Construction of Social Reality. In 1984, he was the Reith Lecturer on the BBC, and he has appeared frequently on U.S. public television. He has been a Guggenheim Fellow and twice won a Fulbright Award. In 1990 he was President of the American Philosophical Association. He has been a member of the American Academy of Arts and Sciences since 1977. He is currently a council member of the National Endowment for the Humanities. His works have been translated into twenty languages. 01998 The Teaching Company Limited Partnership 1 The Philosophy of Mind Table of Contents Professor Biography 1 Course Scope 3 Lecture One: Dualism: Descartes' Legacy 4 Lecture Two: Alternatives to Dualism: Materialism and Its Discontents 6 Lecture Three: Strong Artificial Intelligence 9 Lecture Four: The Chinese Room Argument and Its Critics 11 Lecture Five: Can a Machine Think? 13 Lecture Six: Is the Brain a Digital Computer? 16 Lecture Seven: Some Solutions to Descartes' Problems 18 Lecture Eight: The Structure of Consciousness 20 Lecture Nine: How to Study Consciousness Scientifically 22 Lecture Ten: How the Mind Works: An Introduction to Intentionality 25 Lecture Eleven: The Structure of Action and Perception 27 Lecture Twelve: The Construction of Social Reality 29 Bibliography 31 ®1998 The Teaching Company Limited Partnership The Philosophy of Mind Course Scope: In any intellectual era there are certain overriding problems that form the horizon of intellectual life. In our era the leading problem is how to account for our commonsense conception of ourselves as conscious, free, mindful, rational agents in a world consisting entirely of mindless, meaningless, blind, purposeless physical particles in fields of physical force. This problem is manifest in countless ways. How do the social sciences relate to the natural sciences? What is the nature of mental illness and how does it relate to physical illness? Can we really discover laws of human behavior analogous to the laws of physics? The central problem area, however, lies in the philosophy of mind. What is the nature and structure of the human mind and how does it relate to the rest of reality? The aim of this course is to introduce the student to some of the leading issues in the philosophy of mind and above all to enable the student to think about these problems for himself or herself. ®1998 The Teaching Company Limited Partnership 3 Lecture One Dualism, Descartes' Legacy Scope: To understand contemporary discussions in the philosophy of mind, we need to know something of their ancestry. The modern conception of the philosophy of mind begins with the work of Rene Descartes (1596- 1650), a French philosopher who articulated a crucial metaphysical distinction between two kinds of substances, mental and physical. This view, called "dualism" or sometimes "psycho-physical dualism," survives to the present day. It is, however, subject to decisive objections. Historically, those who reject it typically adopt some version of "monism," the view that there is only one kind of substance in the universe. The two most common monisms are idealism, the view that only mental reality exists, and materialism, the view that only matter exists. Today materialism is dominant in science as well as in philosophy, and the history of the philosophy of mind is in large part an attempt to get a version of materialism which is not subject to decisive objections. Outline Descartes' Dualism A. There are two kinds of substances in the world, mental and physical. 1. The essence of the mental is "thinking" (= consciousness). The essence of the physical is extension (= having spatial dimension). B. The mental and the physical have other distinguishing features. 1. Minds are indivisible (hence indestructible), while bodies are infinitely divisible. 2. Minds are free, while bodies are determined. 3. Minds are known directly, by way of "cogito, ergo sum." Bodies are known indirectly. C. Six Difficulties with Cartesian Dualism 1. The most important problem is interaction: How can the mind and the body ever interact? How can one causally affect the other? 2. Freedom of the will. If the mind is free, but the body is determined, it looks as if the freedom of the mind makes no difference. 3. Other minds. How is it that I can know that other people have minds, since the only mind to which I have direct access is my own mind? 4. Skepticism in general. If I am locked in my own experiences, how can I ever really know anything of the external world? 5. Sleep. How is it possible that people can be totally unconscious, if a person consists of a mind, and mind is essentially conscious? 0 1998 The Teaching Company Limited Partnership 6. Animals. Animals behave as if they had minds, but if so they would have to have immortal souls because minds are indestructible. D. There have been various attempts to solve these problems within the Cartesian framework. All of these attempts have failed. Recommended Reading: Searle: Minds, Brains and Science, (Chapter 1) Descartes: from Meditations on First Philosophy, Meditations II and VI. (in Rosenthal, ed.) Ryle, G. The Concept of Mind, Chapter 1, "Descartes' Myth" (in Rosenthal, ed.) Questions to Consider: 1. What is Cartesian dualism? 2. What sorts of problems does dualism pose for a theory of mind? 3. How do dualists attempt to solve these problems? ®1998 The Teaching Company Limited Partnership 5 Scope: This lecture discusses the history of doctrines in the philosophy of mind that have constituted a response to Cartesian dualism. It is generally assumed that property dualism encounters many of the same difficulties as substance dualism and for that reason is not acceptable. That leaves monism with two possibilities: idealism and materialism. Idealism was influential up to and through the 19th century, but given the enormous success of the physical sciences, it has not seemed an acceptable option in the middle and later parts of the 20th century. Materialism seems inevitable but unattractive. This lecture is mostly about the recurring difficulties with materialism. Outline I. Alternatives to Cartesianism-Property Dualism and Varieties of Monism A. Property Dualism 1. Descartes was wrong to think that there are two kinds of substances. But there are indeed two kinds of properties, mental and physical properties. 2. One and the same body can have both mental and physical properties. B. Varieties of Monism. Within monism, we need to distinguish between those monists who think everything is mental (idealists), and those who think everything is material (materialists). C. Behaviorism: Logical and Methodological Behaviorism distinguished. 1. Methodological behaviorism says we should study behavior as a scientific project in psychology. 2. Logical behaviorism says that any statement about the mind is equivalent in meaning to a set of statements about behavior. II. The Failure of Logical Behaviorism A. Three objections can be raised against logical behaviorism. 1. There appears to be a kind of circularity. Beliefs can only be analyzed presupposing desires, but desires can only be analyzed presupposing beliefs, for example. 2. Behaviorism leaves out the causal component in the relation of the mental to the physical. 3. There are counterexamples of the superactor-superspartan variety. We can imagine someone who acts exactly as if he were in pain, without actually being in pain, and someone who can have a pain without ever manifesting that pain in behavior. 01998 The Teaching Company Limited Partnership III. Physicalism, the theory that mental states are identical to brain states, represents an attempt to improve on behaviorism. A. Type-Type Identity Theories: Every type of mental state is identical with a type of brain state. B. Weaknesses of Identity Theories 1. If there really is a contingent identity between the mental and the physical, then there must be two different sets of features to nail down the identity. But that is property dualism. Attempts to answer this were not successful. 2. Neuronal Chauvinism. It seems too neuronally chauvinistic to suppose that every type of mental state must be identical with a certain type of neuronal physical state. It seems more natural to suppose that every token mental state must be identical with some token physical state. So, type-type identify theory led naturally to token-token identity theory. 3. The common sense objection that we made to behaviorism also applies to type-type identity theory. It seems to leave out the mind. C. Token-token identity theories have many of the advantages of type-type identity theories without many of the disadvantages. But they raise an unanswered question: What do two physical states have in common if they are different physical states, but the same mental state? The answer to this leads to functionalism: They perform the same function in the life of the organism. IV. Three influential arguments have been advanced against identity theories of any kind. A. Thomas Nagel: What it is like to be a bat B. Frank Jackson: What Mary Knew C. Saul Kripke: Necessary Identities V. The functionalist defines mental states in terms of causal relations. Mental states such as beliefs and desires are defined in terms of causal relations between the external input to the system, the internal causal relations among the elements of the system, and the causal output of the system. A. Advantages of Functionalism: Unlike behaviorism, we now have the causal element in the system. Both beliefs and desires can be explained in terms of causation. B. Black Box Functionalism and Computer Functionalism Distinguished 1. Black box functionalism treats the brain as a black box, and it has no theory as to the internal processing. ®1998 The Teaching Company Limited Partnership 7 Lecture Two Alternatives to Dualism: Materialism and Its Discontents 2. Computer functionalism says that the internal processing of the box consists in computations. Computer functionalism is the same as Strong Artificial Intelligence. VI. I summarize the pattern of materialist analyses through behaviorism, functionalism, and computer functionalism. I point out that the general pattern was to treat the problems as a series of technical questions, but each materialistic account seems to have left out some central feature about the mind, such as subjectivity, qualia, or semantic content. Essential Readings: Hempel, C: "The Logical Analysis of Psychology" (in Block, ed) Armstrong, D: "The Nature of Mind" (in Block, ed) Jackson, F: "What Mary Didn't Know" (in Rosenthal, ed.) Kripke, S: Excerpts from "Naming and Necessity" (in Rosenthal, ed.) Nagel, T: "What is it Like to be a Bat?" (in Block, ed) Putnam, H: "Brains and Behavior" (in Block, ed) Searle, J.R.: The Rediscovery of the Mind Chs.1 and 2 Supplementary Readings: Smart, J.C.C.: "Sensations and Brain Processes" (in Rosenthal, ed.) Block, N: "Troubles with Functionalism" (in Rosenthal, ed.) Lewis, D: "Mad Pain and Martian Pain" (in Rosenthal, ed.) Questions to Consider: 1. What is a "type-type" mind-brain identity theory, and how does it differ from a "token-token" mind-brain identity theory? 2. What problems do identity theories, in general, have? 3. What is functionalism? What advantages does functionalism have over physicalism? ®1998 The Teaching Company Limited Partnership Lecture Three Strong Artificial Intelligence Scope: Many people who work in cognitive science and in the philosophy of mind think that the most exciting idea of the past generation, indeed of the past two thousand years, is that the mind is a computer program. Specifically, the idea is that the mind is to the brain as the computer program is to the computer hardware. This view I have baptized "Strong AI," but it is sometimes called "Computer Functionalism." In this lecture I explain the appeal of this view, but I also subject it to a decisive refutation-the "Chinese Room Argument." Outline I. The Theoretical Basis of Strong Al In order to explain the appeal of Strong Al, I have to introduce five somewhat technical notions. A. Turing Machines 1. The idea of a Turing machine is an abstract, mathematical notion. For practical purposes, ordinary computers-the kind that you buy in a store-are Turing machines. 2. The remarkable feature of a Turing machine is that it performs only four operations: Print "0;" erase "1;" print "1," erase "0;" move one square left; move one square right. Modern machines perform these operations at the rate of millions per second. B. Algorithm-an algorithm is a systematic procedure for solving a problem in a finite number of steps. Computer programs are algorithms. C. Church's Thesis-this thesis states that any algorithm can be implemented on a Turing machine. For every computable function, there is a Turing machine that can compute that function. D. Turing's Theorem-this theorem states that there is a Universal Turing machine which can simulate the behavior of any other Turing machine. E. The Turing Test-this test states that if an expert cannot distinguish the behavior of a machine from that of a human, then the machine has the same cognitive abilities as the human. II. Strong AI If we put all these together, we get the idea that the brain is a Universal Turing machine and that human cognitive abilities are computer programs. We test this with the Turing test and come to the conclusion that artificial intelligence is, in principle, capable of creating minds. III. Refutation of Strong Al 01998 The Teaching Company Limited Partnership 9 A. Strong AI and, with it, the Turing test, are subject to a decisive refutation, the Chinese Room Argument. B. The Chinese Room Argument claims that a monolingual English speaker who is locked in a room with a set of computer rules for answering questions in Chinese would in principle be able to pass the Turing Test, but he would not thereby understand a word of Chinese. If the man doesn't understand Chinese, neither does any digital computer. IV. Attacks on the Chinese Room. According to the system's reply, the man in the room does not understand Chinese, but the whole room does. Recommended Reading: Turing, Alan, "Computing Machinery and Intelligence" (Mind 1950, pp 433-60, reprinted in Anderson, ed) Searle, John, Minds, Brains, and Science, Chapter 2 Questions to Consider: 1. What exactly is Strong AI? 2. Why do many people think it is a correct account of the mind? 3. Briefly summarize the Chinese Room Argument. 4. What is the "system's reply?" What is the answer to it? 10 ®1998 The Teaching Company Limited Partnership Lecture Four The Chinese Room Argument and Its Critics Scope: In this lecture we consider some of the implications of the Chinese Room Argument; we answer the most common arguments against it; and we end with a solution to Descartes' mind-body problem. We begin with the distinction between the problem of consciousness and the problem of intentionality. Many people in Al, even in Strong Al, concede that computers are not conscious, but they think consciousness is unimportant anyway. What matters is intentionality, and computers can have intentionality. One advantage of the Chinese room is that it does not depend on consciousness. It applies to intentionality as well. Outline I. Intentionality is defined, and the distinction between consciousness and intentionality clarified. II. The Chinese Room Argument has the simplicity of an obvious counterexample, but in fact, it has a precise logical structure that can be stated in four steps. A. Programs are syntactical. B. Minds have semantic contents. C. Syntax is not sufficient for semantics. D. Therefore, programs are not minds. III. Attacks on the Chinese Room (Continued) A. There is a large number of attacks on the Chinese Room Argument. There must be over two hundred published attempted refutations. In this lecture, I answer the main types of these arguments. 1. The Robot Reply-If the program were implemented in an actual robot, it would understand Chinese. 2. The Brain Simulator Reply-If the program actually simulated the behavior of a Chinese brain, it would understand Chinese. 3. The "Can't Do It" Reply-In real life, it would be impossible to program a human being so that he would pass the Turing test. 4. The "Wait 'til next year" Reply-Maybe better computer technology will enable us to build thinking computers. 5. The analogy with light and electromagnetism reply 6. The "it's not really computation if done consciously" reply B. I answer each of these in detail and discuss the implications of the debate for larger issues in the philosophy of mind. IV. The Solution to the Mind-Body Problem ®1998 The Teaching Company Limited Partnership 11 A. Brains cause minds. B. Minds are features of brains. C. Conclusion: We should treat the mind as a biological problem, as biological as digestion. Recommended Reading: Searle, J.R.: "Minds, Brains and Programs" (with commentaries by critics) (in Rosenthal, ed.) Questions to Consider: 1. The man in the Chinese Room is passing the Turing test in virtue of producing correct output behavior; i.e., presenting the right output symbol for a given input symbol. Does this show that the man understands what the output symbols mean? 2. Is thinking solely a matter of behavioral outputs? 3. How is semantics different from syntax? 4. Can minds have semantic contents that are independent of behavior? 12 ©1998 The Teaching Company Limited Partnership Lecture FiveCan a Machine Think? Scope: The Chinese Room Argument was originally intended as a specific refutation of a very specific thesis in the philosophy of mind, Strong AI. However, it raises a very large number of other issues, and in this lecture I try to go through these in a systematic fashion. Could a machine think? Could an artifact think? Could we build an artificial brain, just as we have built artificial hearts? What is the significance of the Chinese Room Argument? Does it really show that "computers can't think?" What exactly of a general philosophical nature is established by the Chinese Room Argumen