dfranke comments on Three consistent positions for computationalists - Less Wrong
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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.
Or, you could notice that the apparent inexplicability of qualia is a sign that you are confused. ;-)
OK. You understand qualia, Please de-confuse me on the subject.
Have you read the LessWrong Sequences yet?
I have. I don't understand qualia either. Do you have a particular relevant link you were thinking of?
ps: "You should really read the sequences" is telling people to read 1,000,000 words or go away, and as such is functionally equivalent to an extremely rude dismissal. Please don't do that. Link to a particular post if you actually think the pointer is helpful, i.e. make it an actually helpful pointer rather than a functionally rude one.
Some of them. I have read Block, Chalmers, Dennet, Flanagan, Jackson, Levin, Nagel, Searle, etc, etc as well. Which sequence did you have in mind?
My conclusion in the Mary's room thought experiment doesn't challenge either of these versions: something new happens when she steps outside, and there's a perfectly good purely physical explanation of what and why. It is nothing more than an artifact of how human brains are built that Mary is unable to make the same physical thing happen, with the same result, without the assistance of either red light or appropriate surgical tools. A slightly more evolved Mary with a few extra neurons leading into her hippocampus would have no such difficulty.
Incidentally, while agreeing with your main point, I feel I ought to challenge the implications of "more evolved." This has nothing to do with Mary's position on some scale of evolution; she could be "less evolved" and have those neurons, or "more evolved" and lack them.
I should have predicted that somebody here was going to call me on that. I accept the correction.
Mary still doesn't have to make anything special happen to her brain have knowledge of anything else. She can still understand photosynthesis without photosynthesising.
She can understand the sequence of chemical reactions that comprises the Calvin cycle just as she can understand what neural impulses occur when red light strikes retinal rods, but she can't form the memory of either one occurring within her body.
Which, yet again, only matters if there is something special about qualia that requires memory or instantiation in the body to be understood. She can understand the Calvin Cycle full stop.