Tuesday, September 15, 2020

Knowledge of qualia

Consider our old friend Mary, who grew up in a black and white room, learned all of physics, and then saw a red tomato, allegedly learning a new fact about the world, what red looks like. Suppose Mary now went back to her black and white room and returned to contemplating the foundations of quantum mechanics, just as she did before. At that point, clearly Mary knows what red looks like. But unless she is visualizing red stuff, she is not having any red qualia at that point. So:

  1. One can know what red is like without having any red qualia.

Moreover, presumably whatever state her mind has—regardless of whether the mind is physical or not—in her black and white room after seeing the red tomato is a state that could have been induced in her (by a neurosurgeon or a demon) without her having had any red qualia. One might worry whether that induced state would count as knowledge, but if one adds that she gets testimonial evidence that her mental representations of qualia are correct despite based on false memories, it could be knowledge. Thus:

  1. One can know what red is like without having or having had any red qualia.

It is possible to agree to (2) while holding that the knowledge of qualia argument against physicalism is a good argument. For one might hold that the state of mind that allows for (2) is not a state that can simply come from learning all the physical facts. It is a state that might require some kind of neurosurgical or supernatural intervention. But it seems to me that when one accepts (2), it becomes significantly less plausible that one cannot learn what red is like just by learning all the physical facts.

There is another move the defender of the knowledge argument can make. They can deny (1) and (2), holding that when Mary is back to thinking about quantum mechanics, she doesn’t know what red is like, but that we are inclined to incorrectly say that she knows it because she has the skill of coming to know it at a moment’s notice by visualizing something red. This is a good move, but it has a pitfall: it makes knowledge of what red is like significantly disanalogous to ordinary knowledge, such as of multiplication tables, which one has even when it is merely dispositional, when one is not thinking about it. But if knowledge of what is red is like has this significant disanalogy to ordinary knowledge, that makes it less likely that it is factual knowledge—which the argument requires it to be.


B. FORSTADT said...

I have a very impoverished olfactory imagination - try as I might, I can’t imagine what apples smell like. Of course, when I do actually smell apples, they are instantly recognizable.

Do I know what apples smell like? It’s hard for me to give a straight answer. On the one hand, I can identify apples by smell, and when I do, I seem to experience associated qualia. On the other hand, my access to what apples smell like feels quite different from my access to other knowledge. I can only “retrieve it” in certain situations. If I think to myself “What is the capital of the United States?” the answer pops out - not so for “What do apples smell like?”. Perhaps it is better to say I forget what apples smell like when I’m not smelling them. Other people have aphantasia - they can’t visualize things. Perhaps they don’t know what red looks like when they’re not experiencing it.

Suppose a neurologist implanted in me the ability to recognize by scent some kind of exotic fruit I have never smelled before. It seems strange to say that I have learned a new fact, or that my epistemic situation has improved somehow. I wouldn’t be able to imagine what it smelled like it even if I tried. I have gained a new ability though.

Alexander R Pruss said...

Very interesting.

Normally, I can't visualize specific faces, even of my closest family members. (On rare occasions, I get a brief mental flash of a distorted version of one of their faces. And if I make a mental effort, I can visualize parts of generic faces: a fat nose, or a pair of eyes above a nose bridge, though I don't think I can visualize the eyes together with the whole nose.) I have no trouble recognizing them, though.

The inability to imagine a face seems to me to be just that: an inability, akin to the inability to draw a face. (Interestingly, I can draw a face that is recognizably in the genus homo, maybe even in the species homo sapiens, though not recognizably any particular human.)

Do I know what my family members look like? One test of whether someone knows what someone looks like is whether they can pick them out of a lineup. I wouldn't have any trouble with that. But another test is whether they can describe them. And I'd do VERY poorly there.

ARaybould said...

Your argument concerning point 2 is very interesting, as I see it as a very plausible argument against accepting the knowledge argument's conclusion.

Firstly, it is It seems entirely plausible that a neurosurgeon could bring about the relevant mental state, for example by stimulating the optic nerve to fire in the same way it would on Mary seeing a red tomato, or by stimulating the nerves it connects to in the way they are stimulated by the optic nerve. It is also plausible that if the neurosurgeon brought about all, and only, the persistent physical changes that would result from Mary seeing a red tomato, the result would be the same.

Conversely, it is implausible that Mary would be able to do this from any amount of studying books. We do not know how to address specific neurons in our brain to bring about specific changes through mental effort, and there is no reason to believe that the brain is wired up in a way to enable this.

So, Mary could know at least as much as the neurosurgeon about what changes to make in her brain to bring about this change, yet be unable to bring them about. She could know all the relevant physics, yet still learn something from seeing colors for the first time, without this being a challenge to physicalism of the mind.