The following abridged version is from 1000wordphilosophy.com. For the full 1000 words see link at the bottom.
"In philosophy of mind,
physicalism is the view that mental states, like beliefs, feelings and desires, are nothing over and above the physical states of the brain: we don’t have souls or any non-physical features, and so all facts about our minds are, at bottom, physical facts. Physicalism is the theory of mind that many argue is most consistent with a scientific understanding of the universe.
But imagine this:
Mary is a brilliant super-scientist who has never left her black-and-white room, in which she has never seen colors. She has complete physical knowledge, that is, scientific knowledge expressible in physical and functional terms, about human color vision from books and black-and-white television. So, she knows every
physical fact about human color vision.
One day, however, she leaves the room and sees a red tomato (she knows that tomatoes are red). She exclaims “
This is what it is like to see red!
This is what people experience when they see red!”
Now, we have an argument against physicalism, known as the
knowledge argument: Mary apparently learns a new fact about human color experience. But she already knew all the
physical facts before she left her room. So, what she learns must be a
non-physical fact. Since there are non-physical facts, physicalism is false.
Let’s consider four of the most prominent responses to this argument.
1. The Ability Hypothesis
According to the
ability hypothesis, Mary does learn something when she sees red, however, what she learns is not a new
fact, but it is
know-how; she just acquires new cognitive abilities. Knowing what it is like to have a certain experience, on this view, consists in the possession of the abilities to recognize, imagine, and remember the relevant experience. If what Mary learns is just know-how, which doesn’t involve a new truth, then her pre-release knowledge can still be complete.
A problem with the ability hypothesis, however, is that Mary does seem to learn a new truth when she sees red, beyond mere know-how. When she says “
This is what people experience when they see red!” she states a true belief, which she didn’t have before seeing a red tomato.
2. The Acquaintance Hypothesis
A similar response is that Mary doesn’t learn a new truth but she gains nonfactual
acquaintance knowledge.
Suppose I ask you whether you know Oprah, and, as an answer, you give me some facts about her. But, then, I say “No, what I am asking is do
you know her?” I am asking whether you know her
personally. According to the acquaintance hypothesis, Mary comes to know what it is like to see red in this sense of “know.” To know what it is like to experience a mental state is just to experience that mental state. Then, of course, Mary cannot know what it is like to see red before she leaves the room, but this doesn’t mean that there were some facts that she didn’t know. It is possible to know all the facts about Oprah without knowing her personally, and it is possible to know all the facts about the red seeing experience without actually having that experience.
The acquaintance hypothesis, however, like the ability hypothesis, denies that Mary learns a new truth, so the above objection to the ability hypothesis can be raised against it also.
3. The Phenomenal Concept Strategy
According to this view, Mary’s new knowledge is about the physical facts that she already knows about. First-personal knowledge of experiences involves
phenomenal concepts, concepts that directly denote subjective experiences, and phenomenal concepts can only be acquired by subjective experience.
When Mary sees red, she says, “
This is what it is like to see red.” Let’s say physicalism is true and the experiential redness Mary is talking about is actually a physical property of the brain. Let’s call this physical property “R.” So, what Mary says is equivalent to this: “R is what it is like to see red.” “
This” in her remark expresses a phenomenal concept. So, what Mary learns upon seeing red is not a new truth, but a new way of apprehending a physical truth that she already knew. By analogy, this is just like “Superman can fly” expressing the same fact as “Clark Kent can fly."
The main difficulty with the phenomenal concept strategy is to explain the nature of phenomenal concepts in completely physical terms, given that phenomenal concepts seem to involve subjective experiences from the first-person perspective.
4. The No Learning Objection
Some physicalists argue that the intuition that Mary learns something new upon seeing red is
prima facie powerful only because we lack adequate understanding of what complete physical knowledge would be. According to them, even if we cannot see how, Mary would be able to deduce whatever fact is expressed by “
this is what it is like to see red” from physical knowledge.
However, many physicalists disagree. They maintain that Mary learns something when she sees red for the first time and that, even though this is not a new truth, it is something new (either know-how or acquaintance knowledge or a phenomenal concept) that is not deducible from her physical knowledge.
5. Conclusion
The knowledge argument is one of the most influential arguments against physicalism. Explaining the nature of our subjective knowledge of our experiences in physical terms seems to be very difficult, and, simply put, the knowledge argument says this: if our experiences were physical, then explaining our knowledge of them wouldn’t be this difficult."
Any thoughts relevant to the arguments of this post?
The Knowledge Argument Against Physicalism
