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.

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