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State and evaluate the Knowledge Argument against physicalism1
Statement of the Argument
- The best way of introducing the argument is by way of example.
- Frank Jackson, in the paper "Jackson (Frank) - Epiphenomenal Qualia", gives two illustrations of this argument. The first (“red Fred”) is an example of exceptional colour discrimination, whereas the second (“red Mary”) involves sensory deprivation.
- Red Fred
- Fred can finely distinguish things of different colours, demonstrated by his objective ability to sort red tomatoes repeatedly and identically into two groups.
- He sees two colours, red1 and red2, where the rest of us see only one. He cannot teach this discrimination, which he takes to be red1 / red2 colour-blindness in the rest of us. Physiological investigation shows that Fred’s optical system can indeed distinguish two groups of wavelengths in the red spectrum as well as the rest of us can distinguish yellow and blue.
- We have to admit that Fred can really see one more colour than the rest of us. To resist this view is to be like those in H G Wells’ The country of the Blind where the faculty of sight on the part of those who could see was ridiculed and the advantages conferred by sightedness (not falling into ditches, for instance) were put down just to those special skills themselves.
- We do not know what kind of experience Fred has when he sees red1 and red2, and no amount of physical information about Fred’s brain or optical system can tell us. Information about cones tells us nothing about his colour experience. Because, despite knowing all the physical information, including knowledge of Fred’s body, behaviour, dispositions, physiology and history, we still don’t know everything about Fred, physicalism leaves something out.
- This point is emphasised by considering that, even were we able to make everyone (or by transplantation, one particular person) see like Fred, then this would only go to show that beforehand there was something about Fred we didn’t know (because we came to know it).
- Beforehand, we had all the physical information about Fred, but after the operation, there is more we know about Fred’s visual experience, so physicalism must be incomplete.
- Red Mary
- Mary, a brilliant scientist, has normal colour vision, but is forced to investigate the world from a black and white room via a black and white television. She’s a specialist in the neurophysiology of vision, and knows which wavelengths of light cause us to use which colour-words, including all the mechanical workings that cause us actually to utter these words.
- However, when Mary is freed from her room, she will learn something more about the world and our experience of it. Prior thereto, despite all the physical evidence, she did not have all the knowledge, so physicalism is false.
Evaluation of the Knowledge Argument
- Jackson’s View
- Jackson has a robust view of the knowledge argument. In addition to vision, it applies similarly to the other senses and for mental states with phenomenal features or qualia. So, qualia are left out. The polemical strength of the knowledge argument is that it is hard to deny the claim that we can have all the physical information without having all the information there is to be had. So, he claims, physicalism is false. He thinks there are more straightforward arguments against physicalism – for instance, that nothing of a physical sort captures the smell of a rose, so physicalism is false. However, while thinking this argument perfectly good, though not logically valid, and having a premise that is to him intuitively obvious, he finds it polemically weak because not everyone does find the premise intuitively obvious. We need to find an argument with premises obvious to as many as possible. Jackson thinks the Knowledge Argument is the best bet.
- However, before we can properly evaluate the effectiveness of the argument, we need to get clear in our heads what physicalism is, or, rather, which versions, if any, the Knowledge Argument is effective against.
- What is Physicalism?
- In order to understand the claims and intuitions of physicalism, we need to understand the aims and scope of physics. The following account is substantially due to Tim Crane2.
- Physics aims at what Quine calls full coverage of the properties and behaviour of anything that has spatio-temporal position, using its quantitative techniques and categories of force, mass, etc. The generality of physics claims that all objects and events in space-time have physical properties and that their behaviour is described or governed by the laws of physics. Physicalism is an extension of the monist principle of the generality of physics in claiming that this is the whole story.
- The whole story does not just mean full coverage but is a doctrine about causation, that everything physical that happens or is an effect is a result of purely physical causes in accord with physical law. According to David Papineau, the completeness of physics states that every physical event has a physical cause which, given the laws of physics, is sufficient to bring it about. In order to avoid getting tangled up in issues over determinism, this ought strictly to be expressed, as Papineau points out, as that every physical event is determined, or has its chance determined, by purely physical causes in accord with physical law.
- The completeness of physics doesn’t mean that physics is complete as a science, just that physical causes (were we to know them all) are sufficient to bring about physical effects.
- A yet stronger claim is the explanatory adequacy of physics. According to David Lewis, this is the claim that there is a body of scientific theories similar to those currently accepted that provides a true and exhaustive account of all physical phenomena. These theories are hierarchical and cumulative, resting on a few simple laws of particle physics similar to those currently accepted by theoretical physics.
- We may reject this latter claim on the reasonable grounds that the special sciences have their own vocabularies and explanatory domains that neither can or need be reduced to physics-talk. However, the explanatory autonomy of biology, say, is compatible with both the generality of physics and with the completeness of physics. This is because, on the one hand, biological interactions take place among things with physical properties and do not break the laws of physics and, on the other, biological occurrences have physical causal histories that fix their occurrence.
- According to the completeness of physics, all that is required to explain all the physical effects in the universe are the initial conditions and the laws of nature.
- What physicalism, or the completeness of physics, comes down to depends on the meaning of physical. Crane has treated it as defined by the scope of science aiming at full coverage. Thus, what the physical is like is an empirical matter, unlike the old materialism, which had a relatively a priori view of the properties of matter, which modern physics has shown to be incorrect in almost every respect.
- So, is the content of physicalism open ended? The notion is problematical, whether fixed by contemporary physics or some ideal future physics. The reason is that, in the first case, it is false while, in the second case, it is empty.
- Physicalism’s response is that we should commit ourselves only to the existence of a particular kind of thing, that which physics says there is. As physics advances our metaphysical commitments may change, but we have no standard other than physics for deciding what exists.
- This view restricts what physicalists should permit themselves to deny. Crane’s example is in denying the existence of ghosts or the paranormal. If, as seems somewhat unlikely, irreducible ghosts or telekinesis came to be seen as essential to explain the phenomena, then they would be absorbed into the ranks of the physical. While physicalists can rightly ignore these possibilities, this view does leave the physical rather open-ended as we can’t say a priori what the physical is.
- Physicalists think of their doctrine as substantial and informative, so alternative definitions such that the physical is what exists in space and time, or that is causal, can be ruled out since they would make physicalism trivially true even of a substance-dualist position.
- The completeness of physics allows physicalists to make metaphysical claims so that physicalism is not to be empty of content. Physics, as it is likely to remain, attempts explanations of things in terms of dynamical equations and a limited number of concepts such as force and charge. The metaphysical generalisation of this is the completeness of physics.
- The completeness of physics is essential to physicalism, which allows physics a unique ontological and epistemological position. To deny it is to claim that there could be causes that are not the subject of physical science.
- Getting back to Fodor’s second objection to mental causation of the physical, his point was that it would violate conservation laws. Seen as an expression of the completion of physics, the reason is that any physical effect must have a physical cause, and consequently that any mental causation would have to introduce more energy into the world, so violating the conservation laws.
- Is the Knowledge Argument Effective?
- It would take us too far out of our way to attempt an explanation of how physicalism accounts for mental phenomena, other than as it is impacted by the Knowledge Argument.
- It’s worth restating the Knowledge argument in propositional form:
- Physicalism implies that all facts are physical facts
- The examples in the Knowledge argument show that there are more facts than physical facts
- Physicalism is false
- A response is that knowledge ascriptions in the examples don’t supply factual knowledge, so there is no proof that the subjects of our thought experiments learn new knowledge (and hence that premise (B) above is false).
- However, we can also argue that knowledge is irrelevant to physicalism, since we could argue that knowledge of physical facts does not entail knowledge of mental facts, even though, according to physicalism, physical facts entail mental facts (in that mental facts are constituted by physical facts).
In-Page Footnotes:Footnote 1:
Footnote 2: Ie. "Crane (Tim) - Elements of Mind - An Introduction to the Philosophy of Mind", 1991, Chapter 2 ("Crane (Tim) - Body"), §12.
- Originally, this essay was only available as a PDF, see File Note (PDF).
- It has now been converted to Note format.
- The original essay (ie. this version) was written in May 2002.
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