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Thursday, May 29, 2008

On Frank Jackson's Knowledge Argument: A Defense of Science

The knowledge argument begins with a compelling scenario. Imagine Mary, a scientist confined to a black-and-white room. She has always been in this room, and so has never known the experience of color vision. The room contains a black-and-white television through which Mary interacts with the rest of the world. In this way she has learned all of the physical facts of color vision. Yet, she has never experienced color vision directly.
This scenario was first described by Frank Jackson in the 1980s, and was designed to raise the question: If Mary leaves the black-and-white room, will she learn something new about color?
The intuitive answer is, yes, Mary must learn something new. She will learn what it is like to see colors. The implication is that there is more to be known about color vision than what can be contained in the scientific literature. The experience of color vision must include some kind of special knowledge, something which is not described by the physical facts.
The knowledge argument is made against the philosophical doctrine known as physicalism, an idea which lies at the heart of scientific thinking. Physicalism states that everything is physical; or, in other words, that every fact about existence is a fact about the physical world. If The Knowledge Argument is correct, then there are facts which are not physical—facts which cannot be known through science.
The knowledge argument can be broken down into the following set of premises and conclusion:
P1: If a person has all of the physical facts about color vision, then they have all of the facts about color vision. (Definition of physicalism)
P2: Mary has all of the physical facts about color vision.
(Assumption)
P3: Mary learns new facts upon release from her room.
(Intuition)
Conclusion: Since Mary learns new facts, she did not have all of the facts about color vision. Therefore, the physical facts are not all of the facts.
The conclusion contradicts the first premise, but this does not mean that the first premise is necessarily invalid. It only means that at least one of the three premises is invalid.
For decades, there has been philosophical debate over which premise to abandon. The options are generally considered to be either P1 or P3. Since P3 seems intuitively obvious, supporters of the knowledge argument directly attack P1. In order to avoid a logical contradiction, they say, we must abandon physicalism.
However, some notable philosophers, such as Daniel C. Dennett, have diligently argued against P3. Dennett does not question the intuitive appeal of P3; rather, he questions the willingness to trust that intuition. We do not know what life would be like for a person who had all of the facts about color vision; therefore, we cannot assume Mary would learn something new upon leaving the black and white room. Our intuitions are often valuable, but they can also be misleading. (See the discussion in Dennett's book, Consciousness Explained.)
Dennett's argument is compelling, but it does not provide a decisive answer against the challenge produced by the knowledge argument. The best Dennett can say is, we don't know. This makes the decision of which premise to discard a matter of personal opinion, and not argument or evidence.
In all of the literature, I have yet to see an interrogation of P2. (Footnote: Since first publishing this blog entry, I have been informed that much criticism of P2 does exist in the literature.) Yet, the most obviously problematic premise in the Knowledge Argument is neither P1 nor P3; it is P2.

Physicalism entails the notion that every fact about existence is a physical fact. It does not stipulate that one can have all the facts about any aspect of existence. Physicalism does not require, or even suggest, P2.
Furthermore, P2 is not reconcilable with a pragmatic understanding of science and knowledge. When Jackson claims that Mary has “all the physical facts” (P2), he is reaching beyond physicalism and towards a view of science and knowledge which we should be wary to embrace.

We have no way of contextualizing the notion of “all of the facts” about something such as color vision. Without any such limitations to guide our thinking, "all of the facts" is not a well-defined concept.
Consider the extent of the facts alluded to in the knowledge argument. “All of the facts” about color vision must include all of the facts about how people report color vision; facts about how color vision compares to other forms of sensory input; facts about how color vision varies among all possible species, and all possible members of all possible species, including all possible life forms on all possible planets.
How does one draw the line between "all of the facts" about color vision and "all of the facts" about every subatomic particle that has ever and will ever exist? In short, how can we draw a sharp line between "all of the facts" about color vision and "all of the facts," period?
There is no conceivable limit to the connections and comparisons we can draw between objects and events. If there is a limit, it is not one we can know. “All of the facts” about color vision, or anything else, extends beyond all conceivable spatial, temporal and logical boundaries. Knowledge of “all of the facts” therefore implies omniscience, an accomplishment no scientist or philosopher can or should presuppose.
The notion of omniscience runs counter to scientific thinking. Scientific knowledge is about creating theoretical frameworks for making testable predictions. It does not aim at describing every fact about existence. Rather, we rely on science to navigate in a world where having “all of the facts” is not a conceivable option.
We cannot entertain a notion of omniscience unless we completely abandon science as we know it. This is precisely what P2 would have us do, and it is thus not surprising that the Knowledge Argument leads to a contradiction.
The failure of the knowledge argument is instructive. It points to a common misunderstanding of science and knowledge which unfairly pits physicalism against our intuitions about knowledge and experience. Perhaps by overcoming this misunderstanding, philosophers will develop and establish a firmer understanding of science and philosophy.

I present and critique a version of the Knowledge Argument that does not rely on P2 here:  Omniscience, Testability and The Knowledge Argument.