Lecture 10.2 IDENTITY THEORY

Transcription

1 TOPIC: Lecture 10.2 IDENTITY THEORY Armstrong s argument for Identity of mind and brain. KEY TERMS/ GOALS: The story of Phineas Gage. Physicalism. READING: Armstrong, That nature of mind, in Perry, p (skim the article). CONTENT: Recall that Descartes argument for dualism is: P1. The mind has properties of non-extension and indivisibility. P2. The body (brain) is extended and divisible. P3. Leibniz law is true (assumed inference). C. Therefore the mind and body are not identical. Dualism argues that the mind and body are separate because each contain different properties. I will offer a counterexample of a true story of a man who sustained brain injury, and subsequently altered the properties of his mind. Then I will explain Identity theory, the view that the mind and brain are identical. THE STRANGE CASE OF PHINEAS GAGE. The story of Phineas Gage is one of the first recorded cases of brain injury where doctors suspected that damaging the brain will damage the mind. Previous to the late 1800 s doctors and early psychologists (psychology was not an established field yet) suspected that the mind and brain interact, but they had no evidence. A railroad foreman, Phineas Gage was known to be well-respected, hard-working, and a kind gentleman. In 1848 he had an accident while tamping an iron rod into a railroad track. There was an explosion, and the rod, which was an inch in diameter, and about three feet long, shot through Phineas Gage s face, from the bottom of his jaw up through the frontal cortex of his brain. A newspaper reports that the powder exploded, carrying an iron instrument through his head an inch and a fourth in circumference, and three feet and eight inches in length, which he was using at the time. The iron entered on the side of his face, shattering the upper jaw, and passing back of the left eye, and out at the top of the head... The most singular circumstances connected with this melancholy affair is, that he was alive at two o clock this afternoon, and in full possession of his reason, and free from pain. (from Free Soil Union, September 1948). It is reported that co-workers heard the explosion, and then a whistling sound, which must have been the rod shooting through the air. Here is a famous diagram depicting where the rod shot through his face based on postmortem dissections:

2 Phineas Gage never lost consciousness, and had no obvious physical symptoms other than shock. But after several weeks, people complained that he was no longer Gage. Gage s Doctor described Gage s post accident personality as: Fitful, irreverent, indulging at times in the greatest profanity which was not previously his custom, manifesting but little deference for his fellows, impatient of restraint and advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operation, which are no sooner arranged than they are abandoned a child in his intellectual capacity and manifestations, he has the animal passions of a strong man. (from Damasio H., Grabowski T,. Frank R., Galaburda AM., Damasio AR. (1994). Gage s personality changed. He became crude, uncaring, impulsive, irrational, anti-social. His case lead to the theory that damage to regions of the frontal lobes on both sides causes a defect in rational decision making and the processing of emotion ( The return of Phineas Gage: clues about the brain from the skull of a famous patient. Science. 264(5162):1102-5). Subsequent cases from Frontal Lobotomy surgeries also provides evidence that the Frontal Cortex is responsible for reasoning and social behavior. Frontal Lobotomies 1935: chimps who were neurotic before surgery became more relaxed after it 1930s: Egaz Moniz begins frontal lobotomies in humans (and eventually wins Nobel Prize) 1950s: psychosurgery in vogue; 40,000 frontal lobotomies in North America Prefrontal labotommies no outward signs of emotion no facial expression no feelings toward other people (but still liked her dog) felt empty, zombie-like Other patients lose prosody = emotional component of speech orbitofrontal cortex Patients with damage can remember info but don t have emotions associated with it 32 Damage to the Frontal Cortex causes poor control of reasoning, planning & emotions, disinhibition (i.e. gambling, capricious behavior ), poor mental flexibility( i.e. Inability to plan ahead, poor perseveration: e.g.

3 trouble stopping action once initiated), Personality differences (i.e. it affects social interactions), working memory deficits, and temporal memory / Source memory problems, even though patients may have normal IQ on standard tests. What can we conclude about cases like these? Recall that Descartes thought that the mind is indivisible (i.e. if you introspect on your mind, you only find one WHOLE person s thoughts, namely your own). However, if we grant that damage to certain parts of the brain causes damage to SPECIFIC parts of the mind, then we might wonder if there are aspects of the mind that can be divided. Phineas Gage was only affected in certain areas, namely that of social interactions and planning. Other parts of his mind were unaffected, such as IQ. So we see a correlation between damage to specific areas of the brain, and changes in personality. The theory is that those areas of the brain are responsible for certain parts of one s personality. Descartes premise that the mind is indivisible is unsound. More importantly, cases of brain damage point to a stronger interaction between the mind and the brain. If someone is in a coma or has a stroke, the mind is often significantly altered. One may wonder, then, if the brain just wholly responsible for the mind, that is, if the mind and brain are identical. ARMSTRONG S IDENTITY THEORY. David Armstrong briefly mentions a couple problems with Dualism, and then argues for a position called Identity Theory of Mind, the theory that the mind and body are identical. Physicalism is the doctrine that everything is made up of material matter. In other words, the only ontological things that exist in the universe is material matter, and every phenomenon can, in principle, be explained by physical laws. The Identity Theory is a physicalist theory that argues that humans are physico-chemical creatures that is, they are made up only of physical and chemical materials. There is nothing above and beyond the physical material such as a separate mind substance. Emotions, for example, just are the chemicals in the body that constitute what we call emotions. For example, pleasure just is dopamine and serotonin, and excitement just is adrenalin or norepinephrine. Thoughts are neuron patterns, and pain is a firing of nerves from the skin. PROBLEMS WITH DUALISM. Armstrong critiques dualism in this essay and other essays. I will mention a couple. He says, Yet [dualism] presupposed that one person could in principle never recognize the difference between the rational and irrational utterances issuing from other bodies, since he could never get access to the postulated immaterial causes of some of the utterances. Save for the doubtful exception of himself, he could never tell the difference between a man and a robot. In other words, if dualism is true, then each person s inner mental life is private -- known only to them. But if that s the case, then how can I know that anyone else (besides myself) has a mind at all? We want to think that other people have minds (and that they are not just robots), but dualism offers no solution for assuming this, since we can never SEE other s minds or feel them the way we feel ours. This problem is called the Problem of Other Minds. If Identity Theory is true, however, we can make an argument by analogy. That is, we can say that my brain is made of neurons, and what it is to think is to have a certain working configuration of neurons. If I

4 can think with my neurons, and you have neurons, then by analogy we can say that others are thinking as well. This is a solution to the Problem of Other Minds. As another problem with dualism, Armstrong argues that dualism is not scientific. Recall that Dualism proposes that there is a non-physical substance called the mind. But if it is non-physical, then we cannot test, verify, experiment, or confirm the nature of the mind. The theory of dualism smacks of pseudoscience by proposing theories that cannot be tested, confirmed, or falsified with the scientific method. This is a problem, and Armstrong thinks that the theory of dualism will follow the pattern of other pseudoscientific theories by eventually dying out. As a famous analogy in Philosophy of Science, consider the theory of Vitalism the doctrine that living things contain a nonphysical substance that animates them with life. If we go back in time, we find phenomena that weren't understood scientifically. Take lightning for example. Lightning was thought to be Zeus' thunderbolt. By the 19th century the science of electricity was much better understood and we came to understand that lightning is an electrical discharge. Science was able take a phenomenon that seemed to defy description and show that it can be understood in the framework of physics. In the 19th century we didn't understand what makes something alive. It was proposed that there is some nonphysical substance that animates things with life, namely a substance of Vitality. But in the last 100 years Biology has discredited Vitalism. The discovery of the molecular basis of life has been a triumph for physicalism. We now know that organisms are made of the same thing as anything else, (carbon, oxygen, etc.). Life differs from nonlife because of how the basic physical constituents are organized. So we have two reasons to use science rather than some other field to find out what the nature of relation between mind and body is. Science produces consensus about what is the case, and its doctrine of physicalism has been very successful. The Mind/Brain Identity Theory says that what happened to vitalism will happen to dualism. Both vitalism and dualism argue for non-material substance. Dualism supposes there is a separate nonmaterial stuff that explains our mental life and vitalism supposed there was a substance of Vitality that gave living things their property of life. But since Vitalism has shown to be a false theory, so will Dualism. Science has operated on the assumption of physicalism and been very successful. According to Science there is only one kind of stuff in the world-- material matter. Armstrong says, "If we consider the search for truth, in all its fields, we find that it is only in science that men versed in their subject can, after investigation that is more or less prolonged, and which may in some cases extend beyond a single human lifetime, reach substantial agreement about what is the case" (260). Armstrong is saying something like this: There has been little progress in philosophy in terms of coming to a consensus on lots of issues. The mind/body problem has been debated for hundreds of years. There are practically as many theories of human nature from literature as there are authors. Scientists, might have their disagreements, but they have come to a consensus about so much. Perhaps there is something about the way that science proceeds to make it the best way to find truths. The argument, then, is that since vitalism is not a successful theory, and dualism is like vitalilsm, then dualism will not be successful. The only candidate is physicalism, so we should place our bets on physical theories of the mind. IDENTITY THEORY OF PAIN. As an example of how the Identity theory can be used, we can examine how an Identity Theorists might consider PAIN to be. During the 50's and 60' scientist thought they had discovered the physical basis for pain. They thought they had identified what happened physically to the body when people reported having pain. The experiments looked like this: Doctors would stimulate nerves on the skin by poking the skin, and then they would look at brainwaves and MRI patterns of the brain when people reported having pain. They found certain

5 pathways from the nerves to certain areas of the brain, which they called C-fibers. The hypothesis was that feeling pain is one and the same thing as having c-fibers fire in the brain. It turns out that hypothesis is false (there is little systematic correlation between C-fibers firing and every case of pain) but this didn't worry Identity theorists. Identity theorists are just claiming that feeling pain is identical with some physical state or another. If it is not C-fibers firing, then it is some other physical state. It is for scientist to figure out precisely what that state is. I hope that the example of Pain=C-fibers firing isn t too foreign to consider. We do, after all, think that the activity of the brain represents something about our mental life. If we did not have nerves in our fingers, we would not be able to feel what we touch. Likewise, if we did not have a brain, we would not be able to think, reason, perceive, or be conscious at all. So something about our brain must be identical with activities of our mind. So, too, if we did not produce hormones or neurotransmitters like dopamine, we probably would not feel things like pleasure or excitement. Identity theory, again claims that a complete account of man can be given in purely physico-chemical terms (Armstrong, p. 324). Consider the following analogy. For a long time people used the word "water" to denote various stuffs in the world. At a certain point in the history of science, it was discovered that water is made of H20 molecules. The discover was that water and H20 are one and the same thing. There certainly is a difference between the to pieces of terminology "water" and "h20" The first term as been used by ordinary people for a long time. The second term, was introduced more recently as a part of a scientific theory. Yet it doesn't follow that the terms H20 and water refer to different things. Philosophers who defend the mind/brain identity theory say that the same point applies to the relationship of mental terms and neurophysiological terms. Identity theory predicts that the same thing that happened to water will happen to terms like beliefs, desires, pain, mind etc. Right now we haven't discovered these things yet. So, to say that mental states (events, processes) just are brain states (events, processes), is analogous to saying water just IS H20, or the Tooth Ferry just IS my Mom. We can say Pain just is C-fibers firing (or whatever brain state science will find that correlates/ causes pain sensation). And, being excited or elated just IS what results when adrenelin, seratonin, dopamine is released in your body. His argument is somewhat tricky, because his target is against logical behaviorism, which we did not talk about. I will just summarize what the argument is. He says that his solution (his synthesis between dualism and behaviorism) is that the mind is properly conceived as an inner principle, but a principle that is identified in terms of the outward behavior it is apt for bringing about (263). That is a mouthful, but it basically means that the mind can be thought of as the things that cause behavior. Armstrong argues that mental states are STATES, not just dispositions to behave. He quotes the following passage from Ryle's book (a logical behaviorist): "To possess a dispositional property is not to be in a particular state, or to undergo a particular change; it is to be bound or liable to be in a particular state, or to undergo a particular change, when a particular condition is realised." (The Concept of Mind, p. 43). This would seem to deny that dispostions are physical states. They are just the tendency to be in a state. For example, consider the property of being brittle. On Ryle's account this has nothing to do with the physical structure of the glass, it just means that the glass has a tendency to break under certain conditions. By contrast, Armstrong thinks the disposition for glass to break is a state of the glass. Certain molecular properties that cause the glass to break when it is struck by a hammer or dropped on a hard floor. The reason Armstrong is against logical behaviorism and dispositions, is that he believes that the mind is NOT identical with behaviors/ dispositions. Pain is not just a tendency to wince or cry when a hammer falls on one s foot. It is a

6 STATE the state of feeling pain, of having the adrenelin flow through one s body, or having the nerve s fire. For Armstrong dispositions are particular states. If this is true then we can say that dispositions are actual causes.he thinks something is clearly more is going on than just a tendency. He thinks that a thought precedes action and even causes action. Thought is not identical to thought, it lies behind thought. Armstrong thinks this is a more natural way to think. He says, "If somebody speaks and acts in certain ways it is natural to speak of this speech and action as the expression of his thought." "Thoughts are not to be identified with behavior, we think, they lie behind behavior." "Perhaps mind can be defined not as behavior, but rather as the inner cause of certain behavior." (263). It certainly seems natural to me to say that my thought that there is beer in the fridge CAUSED my behavior of getting up to grab a beer. S, mental states are causes of behavior. Dualists would agree about this point, but behaviorists would not. In fact Cartesian Dualists would think this a fairly trivial empirical claim. Of course our beliefs and desires and hopes and fears cause our behavior. Our first premise is: P1. Mental States (MS) are the inner causes of behavior (ICB). Mental states, such as thoughts or feelings have the capacity to cause behavior such as grabbing a beer or crying. The second premise is based on empirical scientific evidence that behavior is caused by physical states of the body/ brain. That is when I grab a beer from the fridge, the causes of that behavior is identified by the muscle contractions, nerve firings, neuron activity in the brain, release of neurotransmitters and other chemicals, etc. Human behavior is caused by physical activity in the body. P2. The causes of behavior are brain states. That is, the inner causes of behavior (ICB) are brain states (BS). Therefore we can conclude that mental states just are brain states. (MS) = (BS) ARMSTRONG S IDENTITY THEORY: P1. Mental States (MS) are the causes of behavior (IBS) P2. The causes of behavior (ICB) are brain states (BS). Mental states are brain states. MS= BS. You can see that the argument form is: 1. A= B 2. B=C Therefore, A=C. As an analogy consider this argument: P1. Water is the physical correlate of the substance that we call water.

7 P2. The physical substance that we call water is H20 Water = H20 One benefit of Identity theory is that it is an ontologically simpler theory than Dualism. Identity theory only posits one metaphysical substance, namely that there is material matter in the universe, unlike dualism that posits matter and mind. CRITIQUES OF IDENTITY THEORY. How would we test to see if Identity theory is true? Presumably, there are ways of testing the theory at least in principle, since it is supposed to be a scientific theory. But what would the tests look like? I ll offer a possibility: Here is a thought experiment, then, as a possible way to test Identity Theory: Imagine we set up an empirical test of the identity theorists claim. We could insert a probe into the subjects brain that detects c-fibers firing (or some other relevant patterns of neurons). The experimenter occasionally hits the subject's thumb with a hammer. The subject would then yell ouch and report that he is in pain and each time he does so we have data as to whether his c-fibers fired. Suppose we find a perfect correlation between pain reports and c-fibers firing. If there is a correlation between people reporting pain, and C-fibers firing, then does that mean pain just is C-fibers firing? Does that show that identity theory is true and dualism is false? How would we test what love, pleasure, or sadness is? Armstrong himself offered a possible objection to the Identity theory, and then gave a reply. Here is the objection: Consider what happens when you are driving on automatic pilot. This happens sometimes when you drive in your car and you find yourself at home even though you don t remember turning left or right at the correct spots. The objection is that you re MIND must have been doing something that was somehow separate from your BRAIN. That is, if your mind and brain were just identical, then it would not be possible to do things where your mind seemed not to be controlled by your brain. Armstrong replies that the automatic pilot happens because you are attending to things other than what your body is doing. But that doesn t mean that you re attention itself cannot explained physically. Your thoughts can be reduced to neurons in your brain, and so the act of attending is physical. Therefore, the automatic pilot objection fails to show that Identity Theory is false. I leave it to you to come up with other objections to the Identity Theory. DISCUSSION QUESTIONS: Do you think that there is something to pain that goes above and beyond your nerves firing? Do you think there is more to the mind than just brain activity? Explain. Offer critiques of Identity Theory. Do you think that there are ways of confirming Dualism that Armstrong has not thought of? How would we confirm or falsify the doctrine that the mind is separate from the body? What conclusion can you draw from the story of Phineas Gage? Do you think it shows that Dualism is false?