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Peterdjones comments on Three consistent positions for computationalists - Less Wrong
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No it isn't. All it says is that the parts of our brain that interpret written language are hooked up to different parts of our hippocampus than our visual cortex is, and that no set of signals on one input port will ever cause the hippocampus to react in the same way that signals on the other port will.
But if physicalism is correct, one could understand all that in its entirety from a third person POV, just as one can understand photosynthesis without photosynthesising. And of course, Mary is supposed to have that kind of knowledge. But you think that knowledge of how her brain works from the outside is inadequate, and she has to make changes to her brain so she can view them from the inside.
The very premise of "Mary is supposed to have that kind of knowledge" implies that her brain is already in the requisite configuration that the surgery would produce. But if it's not already in that configuration, she's not going to be able to get it into that configuration just by looking at the right sequence of squiggles on paper. All knowledge can be represented by a bunch of 1's and 0's, and Mary can interpret those 1's and 0's as a HOWTO for a surgical procedure. But the knowledge itself consists of a certain configuration of neurons, not 1's and 0's.
No, the premise of the Mary argument is that Mary has all possible book-larnin' or third person knowledge. She is specifically not supposed to be pre-equipped with experiential knowledge, which means her brain is in one of the physical states of a brain that has never seen colour.
No, she is not going to be able to instantiate a red quale through her book learning: that is not what is at issue. What is at issue is why she would need to.
Third person knowledge does not essentially change on translation from book to paper to CD, and for that matter it should not essentially change when loaded into a brain. And in most cases, we think it doesn't. We don't think that the knowledge of photosyhtesis means photsynthesising in your head. You share that the qualiaphobes assumption that there is something special about knowledge of qualia that requires instantiation.
Well, then when she steps outside, her brain will be put into a physical state that it's never been in before, and as a result she will feel enlightened. This conclusion gives us no insight whatsoever into what exactly goes on during that state-change or why it's so special, which is why I think it's a stupid thought-experiment.
It isn't intended to answer your question about neuroscience.It is intended to pose the philosopher's question about the limitations of physicalism. If physicalism is limited, that eventually folds back to your question, since one way of explaining the limitation of physicalism is that there are non-physical things going on.
When she steps outside, something physical happens in her brain that has never happened before. Maybe something "non-physical" (huh?) also happens, maybe it doesn't. We have gained no insight.
If we agree that she learns something on stepping outside we have learnt that a version of physicalism is false.
Can you state what that version is? Whatever it is, it's nothing I subscribe to, and I call myself a physicalist.
There are broadly speaking two versions of physicalism: ontological physicalism, according to which everything that exists is material, spatio-temporal, etc; and epistemological physicalism, according to which everything can be explained in physical terms. Physicalism can be challenged by the inexplicability of qualia in two ways. Firstly, qualia might be physically inexplicable because they are not physical things, which contradicts ontological physicalim. Secondly, the phsyical inexplicability of qualia might be down to their having a first-person epistemology, which contradicts epistemological physicalism. Epistemological physicalism requires that eveything be explicable in physical terms, which implies that everything is explicable in objective, descriptive, public, third-person terms. If there are some things which can only be known by acquantance, subjectively, in first person terms, then it is not the case that everything can be explained in physicalese. However, ontological physicalism could still hold.