Lecture 8 Property Dualism. Frank Jackson Epiphenomenal Qualia and What Mary Didn t Know

Transcription

1 Lecture 8 Property Dualism Frank Jackson Epiphenomenal Qualia and What Mary Didn t Know 1

2 Agenda 1. Physicalism, Qualia, and Epiphenomenalism 2. Property Dualism 3. Thought Experiment 1: Fred 4. Thought Experiment 2: Mary in the Black and White Room 5. Paul Churchland s Objection 6. David Lewis and Laurence Nemirow s Objection 7. Jackson s Replies 8. Other Objections 2

3 Frank Jackson Australian philosopher born in Professor at Australian National University. Interests include the philosophy of mind, epistemology, metaphysics, and metaethics. Frank Jackson actually does not currently accept his earlier positions on dualism that we are reading. 3

4 Physicalism Physicalism is not the noncontroversial thesis that the actual world is largely physical, but the challenging thesis that it is entirely physical. This is why physicalists must hold that complete physical knowledge is complete knowledge simpliciter (Jackson 1). 4

5 Qualia Jackson thinks physicalism is false because it fails to explain qualia (quale is the singular form of qualia): o the qualitative aspects of experience o What it is like to experience something o Raw feels, or phenomenal features I am what is sometimes known as a qualia freak. I think that there are certain features of the bodily sensations especially, but also of certain perceptual experiences, which no amount of purely physical information includes. the hurtfulness of pains, the itchiness of itches, pangs of jealousy, or about the characteristic experience of tasting a lemon, smelling a rose, hearing a loud noise or seeing the sky (Jackson 1). 5

6 Epihenomenalism Epiphenomenalism is the view that mental events are caused by physical events in the brain, but mental events themselves have no causal effects upon any physical events. Epi means above, upon, or in addition to. Mental Event: Pain Mental Event: Jealousy Mental Event: Smelling a Rose Brain Event: Neurons Firing Brain Event: Neurons Firing Brain Event: Neurons Firing 6

7 Property Dualism Jackson is a property dualist rather than a substance dualist. Like Descartes, he thinks that the mind and body are fundamentally different. Unlike Descartes, he doesn t think they must be different substances. Rather he thinks it is enough to distinguish them on the basis of their difference in properties. Physical properties can be discovered through the objective methods of science but mental properties can only be understood subjectively, through first-hand experience. 7

8 An Argument against Physicalism 1. Nothing you could tell of a physical sort captures the smell of a rose, for instance. 2. Therefore, physicalism is false. Is this argument valid? An implicit premise: If there are facts about the mind that no physical facts can tell us about, then physicalism is false. What valid argument form does this argument follow? Modus Ponens. Is this argument persuasive? 8

9 Thought Experiment 1: Fred Fred is able to make color discriminations that we cannot. He sees two colors, red 1 and red 2, when we only see one. He is able to consistently sort ripe tomatoes into two groups one with red 1 tomatoes and the other red 2 tomatoes. What kind of experience does Fred have when he sees red 1 and red 2?...it seems that no amount of physical information about Fred s brain and optical system tells us. We find out perhaps that Fred s cones respond differentially to certain light waves in the red section of the spectrum that make no difference to ours (or perhaps he has an extra cone) and that this leads in Fred to a wider range of those brain states responsible for visual discriminatory behavior. But none of this tells us what we really want to know about his color experience.. We have all the physical information. Therefore, knowing all this is not knowing everything about Fred. It follows that physicalism leaves something out (Jackson 2-3). The qualia of Fred s experience cannot be explained by physicalism. 9

10 Mary in the Black and White Room Mary is a brilliant scientist who is, for whatever reason, forced to investigate the world from a black and white room (Jackson 3). She specializes in the neurophysiology of vision and acquires, let us suppose, all the physical information 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 (Jackson 3). What will happen when Mary is released from her black and white room or is given a color television monitor? Will she learn anything or not? (Jackson 3) 10

11 Mary in the Black and White Room Jackson thinks that when Mary leaves the black and white room, she learns something new for instance, what it is like to see something red. Thought experiments such as Fred and Mary are manifestations of the Knowledge Argument against physicalism. The knowledge argument claims to show that one does not know everything even if one has all the physical information. In particular, one will not know about qualia. Jackson is expressing the worry that someone who tries to understand how minds work using only scientific methods of investigation would miss something important about our mental lives. 11

12 What it is like to be Argument In What is it like to be a bat? Thomas Nagel argues that no amount of physical information can tell us what it is like to be a bat, and indeed that we, human beings, cannot imagine what it is like to be a bat. His reason is that 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 essentially terms understandable equally from many points of view (Jackson 4). 12

13 What it is like to be Argument It is important to distinguish this argument from the Knowledge argument. 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 left ignorant. And if and when we come to know what this property is we still will not know what it is like to be Fred, but we will know more about him (Jackson 4). Knowing that there is something it is like for Fred to distinguish between red 1 and red 2 is not the same as experiencing that difference ourselves, as if we were Fred. But then, what is it like for us to know what it is like for Fred? 13

14 Imagination is Not the Point 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 imagination are not to the point. The contention about Mary is not that, despite her fantastic grasp of neurophysiology and everything else physical, she could not imagine what it is like to sense red; it is that, as a matter of fact, she would not know. But if physicalism is true, she would know; and no great powers of imagination would be called for. Imagination is a faculty that those who lack knowledge need to fall back on (Jackson 5). 14

15 Paul Churchland s Objection Churchland reconstructs Jackson s argument as follows: 1. Mary knows everything there is to know about brain states and their properties. 2. It is not the case that Mary knows everything there is to know about sensations and their properties. Therefore, by Leibniz s Law (if two things differ in properties, then they cannot be identical), 3. Sensations and their properties brain states and their properties. (Jackson 5-6) Churchland objects that Jackson equivocates between two meanings of knowledge in premises 1 and 2. 15

16 Paul Churchland s Objection Churchland distinguishes between two types of knowledge: Knowledge by acquaintance: gained through immediate experience, without requiring any inferences from prior knowledge. Knowledge by description: gained by inference from other known facts. Churchland thinks Jackson equivocates in his use of knowledge, because knowing scientific facts about vision is knowledge by description, while knowing what it is like to see red is knowledge by acquaintance. 16

17 David Lewis and Laurence Nemirow s Objection Lewis and Nemirow give an objection similar to Churchland. They argue that Jackson equivocates between knowledge how and knowledge that. One knows how to perform a skill whereas one knows that some sentence is true. What Mary acquires when she is released is a certain representational or imaginative ability; it is knowledge how rather than knowledge that. Hence, a physicalist can admit that Mary acquires something very significant of a knowledge kind which can hardly be denied without admitting that this shows that her earlier factual knowledge is defective. She knew all that there was to know about the experiences of others beforehand, but lacked an ability until after her release (Jackson 6-7). 17

18 Jackson s Replies In response to Churchland: Churchland s summary is a strawman of 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 question (Jackson 6). In response to Lewis & Nemirow: Mary s shock at seeing red for the first time indicates that she is surprised to discover that the facts about color vision that she could not acquire from her neuroscientific studies were knowledge that, not knowledge how. I grant that I have no proof that Mary acquires on her release, as well as abilities, factual knowledge about the experiences of others (Jackson 7). (Mary is just made-up: we don t know what would actually happen to someone in her situation.) My claim is that the knowledge argument is a valid argument from highly plausible, though admittedly not demonstrable, premises to the conclusion that physicalism is false (Jackson 7). 18

19 Other Objections 1. Is Jackson making a strawman of physicalism? He insists that the truth of physicalism entails that every single fact about the mind could be known by a super-smart neuroscientist. Physicalism though could be true even if no human being can know every single physical fact that explains the mind. 2. Is Jackson begging the question by claiming that what it s like to see red is not a physical fact? Barbara Montero raises this type of objection. If he s using physical fact to denote the kinds of things one can learn via science, then knowing what red is like is not a physical fact according to the current body of knowledge established by science, but perhaps it could fit into the body of knowledge gathered by scientists in the future, after the right technology has developed. Also, if you instead think of physical facts as everything about the world that depends upon or results from physical processes, then knowing what red is like could be a physical fact. 19