The Knowledge Argument
Or: How I Stopped Being a Physicalist and Learned to Love Descartes.
The Knowledge Argument was first proposed by then Cartesian Dualist, now regretful Physicalist, Frank Jackson. Jackson is an Australian philosopher that any philosophy student worth his or her weight in qualia and zombies should know about. The argument itself starts with a thought experiment devised by Frank Jackson and named, appropriately enough, The Mary's Room Thought Experiment. The thought experiment, as it is written in the Jackson article 'Epiphenomenal Qualia' is as follows:
Mary is a brilliant scientist who is, for whatever reason, forced to investigate the world from a black and white room via a black and white television monitor. 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. She discovers, for example, just which wavelength combinations from the sky stimulate the retina, and exactly how this produces via the central nervous system the contraction of the vocal cords and expulsion of air from the lungs that results in the uttering of the sentence ‘The sky is blue’. ... 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, F. 1982)
The argument itself stems from what Jackson believes to be the only appropriate answer to the question posed at the end of the thought experiment. That answer is 'yes, she will learn what colour looks like'.
From this he devises the following syllogism.
P1: The Physicalist states that everything in this world is physical, including the mind.
P2: The Physicalist believes that if one knows all the physical facts, one knows all the facts.
P3: Mary learns all the physical facts in her room.
P4: Upon release Mary learns a new fact.
Therefore: There are more facts than just Physical facts.
Therefore: Physicalism is false.
Seems pretty airtight, right? Wrong. As with all arguments to do with the philosophy of mind there is no satisfactory side. Many philosophers have devised many counter-arguments to Jackson's Knowledge Argument, they are as follows.
The Churchland Arguments
Paul Churchland has multiple arguments, most of which aren't worth mentioning, the two that are worth mentioning are easily refuted by Jackson. The first argument worth mentioning is the 'ridiculously strong' objection. Churchland argues that if Mary were to learn everything there is to know about substance dualism (IE. Ectoplasm, the pineal gland being a link to the soul, the primitive laws that govern mind/body causation) she still wouldn't know what red looks like. Jackson's response is what one would expect: The Substance Dualist's position is that not all facts can be described. The second argument worth mentioning is that Mary could not even imagine what red looks like and so therefore must be missing some vital piece of information. Jackson says that what she can imagine or not is unknowable. You cannot possibly know whether or not Mary can imagine red or not and so it should not even be brought up in the argument. Jackson prefaces his 1985 paper in which he lists Churchlands objections by saying imagination has nothing to do with anything.
The 'Different Types of Knowing' Argument
David Lewis and Laurence Nemirow came up with what is arguably the strongest argument against the Knowledge Argument. They argue that there are different ways of knowing things, on one hand you can know things because they have been described to you. For example, you can know that Vegemite is a black substance that tastes bitter through description, but you cannot know how Vegemite tastes, how to recognize Vegemite, how to discern Vegemite from other foods via description. With the descriptive knowledge that Vegemite is black and bitter one might mistakenly believe that a tall glass of Guinness is Vegemite. Lewis and Nemirow name the two different types of knowledge 'Knowledge that' and 'Knowledge how'. Jackson's response, as usual, is elegant in it's simplicity. He says that when Mary leaves the room and sees colour for the first time she not only learns how to distinguish, say, red from blue but learns that other people see colours in a certain way as well. Funnily enough, neither Lewis nor Nemirow came up with a response to that which is worth mentioning, but 40 years before the Knowledge Argument even existed AM Turing inadvertently came up with a response. AM Turing argued that if something displays the behavior of a conscious being we should assume that it is conscious, for the only evidence we have that other humans are conscious is that they behave as such. If we assume that behavior is not good enough evidence for sentience then we are cornered into an undesirable position of solipsism. He specifically noted that a person could argue that others are conscious by analogy, but that such an argument would be weak because we only have a sample size of one: Ourselves. What Mary would be doing if she assumed she 'knew' that other people saw colour the same as her would be making an assumption about all humans based on a sample size of one. Since there is no specific behavior attributed to seeing specific colour Mary can never know that other people see colours the same as her.
The Slugs In The Tiles Argument
Much like AM Turing's counter-argument against the counter-argument against the counter-argument against the Knowledge Argument (whew!) 'The Slugs in The Tiles' thought experiment, and the argument which is derived from it, inadvertently creates a good position against the Knowledge Argument. The argument was first thought up by Daniel Stoljar as a way to refute people like Chalmers who said 'it is impossible to solve the problem of consciousness or, at the very least, describe consciousness in physical terms'. Stoljar's thought experiment describes a group of intelligent philosopher slugs (slugists) that can only see circles and triangles. They live on a mosaic which has on it triangles and a circle made up of what we would see as different pie-slice shapes (IE An isosceles triangle with a curved bottom.) Being that the slugs are unable to perceive the pie shape, but can see the circle that the pie shapes make up as well as triangles on other parts of the mosaic the slugs each come up with different theories as to what the circle is. The revered slug philosopher Rene' Escartego and his followers say that circles are primitive shapes and come up with ways in which triangles and circles may be linked, some people say that it is impossible to know what the circle is because it's too hard a problem, et cetera. Another philosopher, Frank Jackslug, says that if a slug were put on another mosaic where they learned about all shapes but circles then they would never be able to know what a circle is, but we know that if a slug learned about the pie shapes then they would be able to know exactly what a circle is by imagining several pie shapes next to each other. This argument is not without it's weakness, though. It is hard to imagine that base qualia like 'red' and 'blue' and 'the flavour of Dr.Pepper' are fragmentary in nature. It seems implausible, to say the least, that you could learn how to experience red in fragments.
My position has been, and probably will remain, that this argument (like most arguments against Jack Smart's identity theory) is largely a semantic one. While I can understand what Jackson is getting at it doesn't seem to me to follow from his argument that Physicalism is wrong. I'll put forward a similar thought experiment to iterate my point:
"Kelly Heller can't see, taste, touch, smell or hear. Kelly Heller learns all she can learn in this state (which is essentially nothing). One day, by some miracle of medicine, she has all of her senses restored and begins to learn all these new and fantastic things about the world. Therefore Physicalism is wrong"
I don't think this is a fallacious example of reductio ad absurdum, rather, an appropriate one to show that Jackson's original argument is, in fact, absurd. I don't think a person has to be a substance dualist if they believe that being able to experience qualia precedes being able to know facts about the world. You might be tempted to say 'that means you're not a Physicalist because...' but to me, Physicalism is more about describing why and how consciousness works not how to experience qualia and what experiencing qualia is like.