The Knowledge ARgument

Epiphenomenal qualia (1982)

By frank jackson

in:  Heil, pp. 762-71

Introduction (762)

A. Jackson offers the following argument against physicalism:

1. if you tell him everything physical that there is to say about what’s going on in the brain, you still will not have told him about the hurtfulness of pain, etc. (762, q.v.)

2. (alternatively) nothing you could say "of a physical sort" could capture qualia such as the smell of a rose (762-63)

3. hence, physicalism is false (763)

B. Although he finds this a perfectly good argument, he realizes that it will not persuade everyone

1. the problem is not the validity

2. not everyone will accept the premise that the "qualia" of our sensations or perceptions are not included among the "physical information" about them

C. however, he resists giving the reader a definition of physical (762)

1. although he includes "physical, chemical, and biological" under "physical information"

2. as well as information about the functional role of processes in the nervous system, etc. (q.v.)

D. the "knowledge argument" for qualia in section I is meant to persuade people of this premise (763)

1. he contrasts this with other arguments against physicalism in sections II and III

a. modal

b. “what it is like to be”

2. in section IV, he addresses the worry about how non-physical qualia could interact with the physical world, and argues that it is possible that qualia are epiphenomena

I. The Knowledge Argument for Qualia

A. People vary in their ability to discriminate colors

B. Jackson has us imagine this person Fred who is able to discriminate two different colors of perfectly ripe tomatoes, which he calls red₁ and red₂

1. Fred consistently sorts the tomatoes the same way

a. to him two groups of wavelengths within the red range appear as different from each other as yellow is from blue (763)

b. from Fred’s point of view, we are red₁-red₂ color-blind

2. no "physical information" about Fred’s optic and nervous system will tell us what these 2 different colors look like to him (764)

3. hence, there is something about Fred we don't know, something physicalism leaves out

4. we can imagine also that we learn enough about Fred that we can surgically alter other people so that they can distinguish these colors as well

a. after one has the operation, one knows more about Fred and his color experiences than one did before

b. hence, there is more to know about Fred than the physical information about his brain and nervous system

C. We don't have to imagine someone like Fred with a different perceptual system to make this point -- we can make the same point involving a normal person (765)

D. Mary the neuroscientist

1. learns everything there is to know about the neurophysiology of vision -- that is, all the physical information -- but in a black-and-white environment -(765)

2. Jackson insists that when we release her from this black-and-white environment and expose her to colors for the first time, there is something new that she will learn

3. Hence, there is more than just physical information and physicalism is false

E. one could make similar arguments with respect to the sensory modalities other than vision

F. he concludes that "it is so hard to deny . . . that one can have all the physical information without having all the information there is to have"

G. Questions and Comments: 

1. one problem is that he never actually defines “physical.” So what makes qualia non-physical?

2. but even if we ignore that, and grant him that the physicalist story leaves something out, the question remains, what is it that it leaves out?

a. For Jackson, it’s the qualia

b. but one could also argue that what it leaves out is information about things other than the body, brain, and nervous system, such as information about tomatoes

c. that is, the quale red is physical information about the tomato, not about us

3. one could also say that Jackson’s argument proves too much

a. it would seem to hold equally well against any philosophy of mind, including dualism

b. but if it’s a problem for everyone, it’s no argument against any particular theory

II. The Modal Argument (765)

A. The Modal argument works like this:

1. those who are skeptical about other minds are not making a logical mistake, as no amount of physical information about another person logically entails that they are conscious like us

2. Hence, we can imagine a possible world (that is, logically possible) with beings who are physically just like us except that they lack consciousness (viz., zombies)

3. Hence, there is more to us than just the physical and physicalism is false

B. Jackson seems to find the modal argument against physicalism less persuasive than the knowledge argument (766)

1. the problem with this argument is that some people will deny that there can be physical copies of ourselves that nevertheless lack consciousness (766)

2. Jackson might think that there could be such beings, but only because he already has an argument that qualia are not part of the physicalist account

C. My comments: 

1. it may be logically possible for there to be copies of us who are not conscious. 

2. But I fail to see how a mere logical possibility constitutes an argument against physicalism.

a. perhaps this mere logical possibility tells against a kind of physicalism in which it is claimed that facts about mental life can simply be deduced from facts about biology

b. but physicalism is not necessarily tied to that claim

III. The "What it is like to be" argument (766)

A. this is Nagel's argument that no amount of physical information can tell us what it is like to be a bat, since this can be understood only from the bat’s point of view

B. Nagel's is different than Jackson's argument (767)

1. Jackson was not arguing that we don't know what it would be like to be Fred (767)

a. He was arguing that there was a kind of fact about Fred’s experience we don't know

b. Even if we knew that fact, we still wouldn't know what it is like to be Fred, although we'd know more about him

2. Nagel on the other hand seems to be arguing that we cannot generalize from what our experience is like to what bat experience is like because they are too different from us

a. Jackson doesn't see how Nagel's argument tells against physicalism, since physicalism in no way entails that we should be able to imagine what it's like to be a bat, nor should it (767)

b. Indeed, if physicalism were true, there would be no need to extrapolate from our experience or imagine how Fred experiences colors, because we'd already know (767 q.v.)

IV. The Bogey of Epiphenomenalism (768)

A. for Jackson, there is no good reason to refuse to accept the idea that qualia are causally impotent in the physical world

1. he's not saying that mental states are not causally efficacious, but only certain properties of them, namely, the qualia (768)

2. also, qualia may “make a difference” to other mental states, even if not to the physical world (q.v.)

3. Me: but do these other mental states make a difference to the physical world?

a. if yes, we’re back in the land of the pixies

b. if no, then how is his position any different from classical epiphenomenalism?

B. Jackson criticizes three arguments that are typically given for the causal efficacy of qualia

C. First argument:  that it's just obvious that it's the hurtfulness of pain that makes us avoid pain

1. however, the fact that B usually follows A does not imply that A causes B. 

2. There could be some underlying third cause of both

a. makes an analogy with a movie:  the real cause is not in the movie but in the projector

b. in the same way, there could be a third thing behind both the pain and the behavior

D. Second argument:  the Darwinian argument that qualia must have been naturally selected because they help us to survive in the physical environment.  This could not be if they had no effects in the physical world. (768-69)

1. here we have to be careful about what natural selection is selecting for (769)

2. for example, in polar bears, there is natural selection for a warm coat.  Having a heavy coat is just an unavoidable by-product of that.

3. for the epiphenomenalist, qualia are similarly an evolutionary by-product of something in the brain that is conducive to survival

4. I have a hard time accepting this

a. for example, there is a hypothesis that color vision evolved in primates to distinguish ripe fruits from leafy vegetation

b. Jackson, I presume, would have us believe that primates distinguish fruit from leaves through unconscious neural processes of which the color of that fruit is just a by-product.

c. that suggests to me that we primates could just as easily distinguish the fruit if we were conscious only of black, white, and shades of gray, as long as the information about wavelengths were subconsciously being processed

E. Third argument:  we infer that other people have minds and qualia like our own from their behavior.  We could not do this unless behavior results from qualia (769)

1. but again, there could be some third thing that causes both the behavior and the qualia, so that we can reason from one effect back to its cause, and then back out to another effect

2. for example, a second newspaper will have the same news as the first, without assuming that the second got it from the first

3. in a similar fashion, we can reason from the behavior of others back to their causes and from these causes out again to their other effects, qualia

F. A final objection to epiphenomenalism:  although there are no good arguments against epiphenomenalism, the fact remains that epiphenomena are inexplicable and don't fit in with the scientific way of looking at things (770, q.v.)

1. although this is true, Jackson finds that this objection rests on an overly optimistic view of what it is possible for us humans to understand

2. he claims that epiphenomenal qualia are irrelevant to survival (770, q.v.)

a. natural selection has not favored the ability to figure out how qualia are caused, the laws governing them, or why they even exist (770, q.v.)

b. watch out for the equivocation here, because whether qualia are relevant to survival is a separate issue from whether being able to explain qualia is relevant. We can agree with the latter without agreeing with the former.

3. to explain why he thinks physicalists are overly optimistic, he makes an analogy with imaginary sea-slug scientists and philosophers (770-71)

a. the tough-minded may think their restricted science suffices to explain everything, at least in principle if not quite yet (771)

1.) in weaker moments, they may say that it leaves something out

2.) but they resist this temptation and their tender-minded opponents by arguing that no one has ever shown how this residue fits in with their successful science

b. imagining beings superior to us in the way we are to sea slugs should serve as an antidote to optimism