Some Thoughts on Jackson's Knowledge Argument

In “Epiphenomenal Qualia,” Frank Jackson tries to argue that physicalism is false because it fails to account for the existence of qualia. Jackson offers a thought experiment about a neuroscientist named Mary. Though Mary lives in black and white room and only sees the world through black and white mediums, such as “black and white television,” she knows all the physical facts about color such as the wavelengths of each color and also how the human eye registers these different wavelengths of light as different colors. Jackson then tells us to imagine what would happen if Mary were to step out of her room and see colors. “Will she learn anything or not? It seems just obvious that she will”. After seeing color, Mary will learn what it is like to see color, she will now have experiential, phenomenal knowledge of whichever color she sees, which is something that she could not gather from merely analyzing the physical facts about color. However, if physicalism were true, Mary would already know everything about color since she knew all the physical facts about it. So, “physicalism” must be “false”.

Responding to this argument, David Lewis argues against the notion of “phenomenal information,” by arguing that the “ability hypothesis” can explain the relevant data just as well as the phenomenal information hypothesis while not forcing us to abandon materialism. Lewis grants that experience adds something to us, but argues that when you “have a new experience, you gain abilities to remember and to imagine”. Lewis goes on to identify “an experience” with “the possession of these abilities to remember, imagine, and recognize”. He gives examples of cases where information will not help one to acquire new abilities, such as the inability to wiggle one’s ears, and in such cases it seems that the reason they don’t have such powers is because they haven’t had the experience. Moreover, there are cases where the acquisition of new abilities requires experience: “that’s why music students have to practice”. However, in these cases, it seems hard to separate the acquisition of new abilities with the experience of new abilities. If Lewis’ hypothesis works, then the materialist can safely avoid Jackson’s argument.

I’m very sympathetic to Jackson’s argument and I think that Lewis’ response fails to adequately respond to it. It seems that Lewis’ ability hypothesis presupposes, rather than replaces, phenomenal information. For example, Lewis states that “after you taste Vegemite, and you learn what it’s like, you can afterward remember the experience you had”. It seems that even in this statement, in order to have the new powers of remembrance, one needs to have the phenomenal experience of tasting vegemite. Moreover, it seems that the ability hypothesis fails to fully account for what gives the person new powers. It cannot be physical facts, otherwise Mary, arguably, would be able to remember and imagine the color red simply by knowing the physical facts about the color red; it seems that phenomenal knowledge is the only thing which can ground these new powers. Identifying experience with the acquisition of new powers seems to just beg the question: what caused the acquisition of these new powers?