> Those are two different knowledge domains This is a circular argument: you are arguing that physicalism is not true by assuming that physicalism (which asser

> Those are two different knowledge domains This is a circular argument: you are arguing that physicalism is not true by assuming that physicalism (which asserts that there is only one knowledge domain) is not true. According to a physicalist, perception is a physical process. So are knowing and experiencing and "what it is like". So to a physicalist, someone who, like Mary in the thought experiment, is stipulated to have complete knowledge of all of the physical facts will know "what it is like" to have any perception, because that is part of the physical facts. The only difference is that Mary, before she is released from the room, knows what it is like to see red by a process of deduction--by looking at what physical facts, among those she knows, correspond to her seeing red--instead of by the more usual process of having her retina and optic nerve stimulated in a particular way. To put it another way, Mary, unlike you and me, knows what it is like to see red by imagining it, based on her complete knowledge of all the physical facts. That complete knowledge allows her to put her brain into any state she likes, even in the absence of the external stimuli that would normally be present. Sure, this is farfetched, but so is the premise that Mary has complete knowledge of all the physical facts. But if you grant the premise, you are granting Mary the powers she needs to do the thing that Jackson incorrectly claims she cannot do. > But it'd be rather futile to try to explain seeing the color red to the alien even if we could, because it's irrelevant to them First, seeing red is obviously not irrelevant to Mary, so this argument says nothing about Mary. But second, if the alien has complete knowledge of all the physical facts about human brains, bodies, etc., then seeing the color red is not irrelevant to the alien, because seeing the color red is part of the physical facts that the alien knows. In other words, this hypothetical alien knows things that any "normal" alien would not know, and that changes what is "relevant" to this alien.