PHI 1500: Major Issues in Philosophy

Transcription

1 PHI 1500: Major Issues in Philosophy Session 15 March 26 th, 2015 Philosophy of Mind: Jackson 1

2 Recap: Descartes vs. Ryle Substance Dualism Mind & body exist in two different worlds (mental vs. physical), because they have very different propermes. Behaviorism (Monism) Mind & body both exist in the physical world, Because what we call mental is just a certain set of behaviors. Mind stuff Body stuff behaviors mental processes 2

3 Two Types of Dualism Mind stuff One type of stuff Mental propermes Body stuff Physical propermes substance dualism: says that minds & bodies are two dis:nct types of substances Descartes believed that minds are res cogitans: things that think (think, believe, feel emomons, etc.), whereas bodies are res extensa: things that are extended in space. property dualism: says that minds & bodies are one substance, which has two dis:nct types of proper:es: mental ones & physical ones. Ø Frank Jackson advocates for property dualism. 3

4 Frank Jackson (1943- present): professor at Australian NaMonal University His famous thought experiment about Mary the neuroscienmst funcmons as a counterargument against a monist account of the mind called physicalism: A metaphysical view which says that everything that exists and occurs in our world including our minds can be explained by physical facts,» i.e., facts about the enmmes described by physics (objects, molecules, atoms, subatomic parmcles ),» and facts about principles of interacmon between those enmmes (a^racmon/repulsion, collisions, electric currents, etc.) 4

5 Types of Monism mind stuff body stuff idealism: only mental things really exist. Everything we experience is generated by minds (ours, God s...) We can gain knowledge about minds through a priori reasoning, rather than using empirical evidence. physicalism: only physical things really exist. Predicts that empirical facts gathered through science will tell us everything one needs to know to understand how minds work. E.g., once we know all the physical facts about how color vision works, we will be able to explain everything that could be said about seeing colors. 5

6 Qualia Jackson believes that a physicalist view of the mind is inadequate, because it fails to explain qualia: qualita:ve aspects of our everyday experiences, like the hurfulness of pains, the itchiness of itches, pangs of jealousy, the sour taste of a lemon, the scent of a rose, the volume of a loud noise (1) Jackson says: Tell me everything physical there is to tell about what is going on in a living brain,» the kind of states, their funcmonal role, their relamon to what goes on at other Mmes and in other brains, and so on & so forth, [but] you won t have told me about why all these qualia exist, and why certain objects have the qualia they do. (1) 6

7 Jackson & other philosophers who emphasize the importance of qualia provide the argument: 1. If there are facts about the mind beyond physical facts about the world, then physicalism is false. 2. Nothing you could tell of a physical sort captures the smell of a rose, for instance. 3. Therefore, physicalism is false. (1) Jackson says, By our lights this is a perfectly good argument, because premise 2 is obviously & intuimvely true, for him & other qualia freaks But, There are, unfortunately for us, many who do not find the premise intuimvely obvious. The task then is to present an argument whose premises are obvious to all, or at least to as many as possible. (2) Jackson wants to make this argument more persuasive. 7

8 Thought Experiment #1: Fred Fred has be^er color vision than anyone else on record; he makes every discriminamon that anyone has ever made, and moreover he makes one that we cannot even begin to make. (2) perceptual discrimina:on = reliably idenmfying a difference between two different qualia Show him a batch of ripe tomatoes and he sorts them into two roughly equal groups and does so with complete consistency. We ask Fred how he does it. He explains that all ripe tomatoes do not look the same color to him, and in fact that this is true of a great many objects that we classify together as red. He sees two colors where we see one, and he has in consequence developed for his own use two words red 1 and red 2 to mark the difference. (2) 8

9 Thought Experiment #1: Fred To [Fred] red 1 and red 2 are as different from each other and all the other colors as yellow is from blue. And his discriminatory behavior bears this out: he sorts red 1 from red 2 tomatoes with the greatest of ease in a wide variety of viewing circumstances. (2) Moreover, an invesmgamon of the physiological basis of Fred s excepmonal ability reveals that Fred s opmcal system is able to separate out two groups of wavelengths in the red spectrum as sharply as we are able to sort out yellow from blue. 9

10 Thought Experiment #1: Fred Jackson asks, What kind of experience does Fred have when he sees red 1 and red 2? What is the new color or colors like? We would dearly like to know but do not; and it seems that no amount of physical informa:on about Fred s brain and opmcal system tells us. (3) Suppose that we know everything about Fred s body, his behavior and disposimons to behavior and about his internal physiology, and everything about his history and relamon to others that can be given in physical accounts of persons. We have all the physical informa:on. But we do not know what it is like for Fred to be able to tell red 1 and red 2 apart from one another. Therefore, knowing all this is not knowing everything about Fred. It follows that physicalism leaves something out. (ibid.) 10

11 Thought Experiment #2: Mary Mary is a brilliant scienmst who is, for whatever reason, forced to invesmgate the world from a black and white room, [educated through black- and- white books and through lectures relayed on black- and white television]... monitor. She specializes in the neurophysiology of vision and acquires, let us suppose, all the physical informa:on there is to obtain about what goes on when we see ripe tomatoes, or the sky, and use terms like red, blue, and so on. (3) she learns everything there is to know about the physical nature of the world. She knows all the physical facts about us and our environment (3) If physicalism is true, she knows all there is to know. For to suppose otherwise is to suppose that there is more to know than every physical fact, & that is what physicalism denies. (3) 11

12 Thought Experiment #2: Mary Jackson asks, What will happen when Mary is released from her black & white room or is given a color television monitor? Will she learn anything or not? He answers: It seems just obvious that she will learn something about the world and our visual experience of it.» E.g., she will learn what it is like to see red.» Therefore, there is something one can know about colors which is not a physical fact. Jackson thinks it is intuimvely obvious that Mary learns something new about colors when she sees them for the first Mme. Ø But not everyone agrees that this is the case. Ø Different philosophers report different intuimons about Mary. Video: bit.ly/1gyjsju 12

13 The Knowledge Argument against Physicalism If Mary learns something new when she sees red for the first Mme, then it is inescapable that her previous knowledge was incomplete: Mary did not know all there is to know [about color vision, a mental phenomenon]. But she had all the physical informa:on. Ergo there is more knowledge to have than that, and physicalism is false. (4) Because physicalism says that the physical informamon provides all the knowledge we could have about color vision. 13

14 Some ClarificaMons about the Knowledge Argument Jackson wants to dismnguish the lesson of his thought experiments about Fred & Mary from another related idea, proposed by Thomas Nagel. Nagel proposes that no amount of physical informamon can tell us [human beings] what it is like to be a bat, and indeed that we, human beings, cannot imagine what it is like to be a bat, [because] what this is like can only be understood from a bat s point of view, which is not our point of view, and is not something capturable in physical terms, which are essenmally terms understandable equally from many points of view. (4) Nagel s point is that what it is like to be a certain sort of creature can not be known objecmvely, but only from the subjecmve experience of that creature. 14

15 Some ClarificaMons about the Knowledge Argument Jackson explains, When I complained that all the physical knowledge about Fred was not enough to tell us what his special color experience was like, I was not complaining that we weren t finding out what it is like to be Fred. I was complaining that there is something about his experience, a property of it, of which we were let ignorant. And if and when we come to know what this property is we smll will not know what it is like to be Fred, but we will know more about him. (4)» In short, knowing that there is something it is like for Fred to dismnguish between red 1 and red 2 is not the same as experiencing that difference ourselves, as if we were Fred.» We smll don t have access to Fred s subjecmve experience. 15

16 Some ClarificaMons about the Knowledge Argument The knowledge argument does not rest on the dubious claim that logically you cannot imagine what sensing red is like unless you have sensed red. Powers of imaginamon are not to the point. The contenmon about Mary is not that, despite her fantasmc grasp of neurophysiology and everything else physical, she could not imagine what it is like to sense red; it is that, as a ma^er of fact, she would not know. But if physicalism is true, she would know; and no great powers of imaginamon would be called for. ImaginaMon is a faculty that those who lack knowledge need to fall back on. (5) 16

17 The trouble for physicalism is that, ater Mary sees her first ripe tomato, she will realize how impoverished her concepmon of the mental life of others has been all along. She will realize that there was, all the Mme she was carrying out her laborious invesmgamons into the neurophysiologies of others and into the funcmonal roles of their internal states, something about these people she was quite unaware of. All along their experiences ( got from tomatoes, the sky...) had a feature conspicuous to them but unml now hidden from her. Jackson expresses a worry that someone who tried to understand how minds work using only scienmfic methods of invesmgamon would miss something important about our mental lives. 17

18 ObjecMons to the Knowledge Argument Jackson presents three objecmons made by Paul Churchland (a philosopher at UC San Diego), in order to defend his property dualist view against these objecmons. We ll focus on Objec:on 1: Jackson equivocates between two meanings of knowledge. Churchland summarizes the Knowledge Argument as an applicamon of Leibniz s Law: 1. Mary knows everything there is to know about brain states and their propermes, 2. It is not the case that Mary knows everything there is to know about sensa:ons and their propermes. 3. Therefore, by Leibniz's law, sensa:ons and their propermes brain states and their propermes. Churchland thinks this conclusion is invalid, because premises 1 & 2 refer to two different types of knowledge. 18

19 Churchland dismnguishes between two types of knowledge: knowledge by acquaintance: gained through immediate experience, without requiring any inferences from prior knowledge. e.g.: my knowledge that the projector screen is in front of the board knowledge by descrip9on: gained by means of inference. e.g.: my knowledge that it will be Saturday two days from today. Churchland thinks Jackson equivocates about knowledge, because knowing scienmfic facts about vision is knowledge by descripaon, but knowing what it is like to see red is knowledge by acquaintance. 1. Mary knows [by descripaon] everything there is to know about brain states and their propermes, 2. It is not the case that Mary knows [by acquaintance] everything there is to know about sensa:ons and their propermes. 3. Therefore, by Leibniz's law, sensa:ons and their propermes brain states and their propermes. 19

20 David Lewis & Laurence Nemirow give a similar objecmon: on her release Mary does not learn something or acquire knowledge in the relevant sense. What Mary acquires when she is released is a certain representamonal or imaginamve ability; it is knowledge how, rather than knowledge that. One knows how to perform a skill, like tying one s shoes or making a free- throw, juggling One knows that some proposimon is true. E.g., I know that Barack Obama is the 44 th President of the United States. According to Lewis & Nemirow, a physicalist can admit that Mary acquires something very significant of a knowledge kind... without admixng that this shows that her earlier factual knowledge is defecmve. She knew all that there was to know about the experiences of others beforehand, but lacked an ability unml ater her release. (7) Once she had seen red, she knew how to tell red apart from other colors, to recall what it looks like, to imagine things being red 20

21 Jackson s replies: Churchland s summary misrepresents the Knowledge Argument, which is not about the kind, manner, or type of knowledge Mary has, but what she knows. What she knows beforehand is everything physical there is to know, but is it everything there is to know? That is the crucial quesmon. (7) In response to Lewis & Nemirow: - Mary s shock at seeing red for the first Mme indicates that she is surprised to discover that there was factual knowledge about color vision that she could not acquire from her neuroscienmfic studies. - I grant that I have no proof that Mary acquires on her release, as well as abilimes, factual knowledge about the experiences of others - My claim is that the knowledge argument is a valid argument from highly plausible, though admi^edly not demonstrable, premises to the conclusion that physicalism is false. (8) 21

22 Summary of Jackson s View Jackson s argument against physicalism (a type of monism) commits him to a property dualist answer to the mind- body problem. He believes that: Physical propermes can be discovered through the objecave methods of science. But mental propermes can only be understood subjecavely, through first- hand experience. One type of stuff Mental propermes Physical propermes 22