They're computationally equivalent by hypothesis. The thesis of substrate independence is that as far as consciousness is concerned the side effects don't matter and that capturing the essential sameness of the "AND" computation is all that does. If you're having trouble understanding this, I can't blame you in the slightest, because it's that bizarre.
Yes, I agree that this kind of atomism is silly, and by implication that things like Drescher's gensym analogy are even sillier. Nonetheless, the black box needs a label if we want to do something besides point at it and grunt.
I should have predicted that somebody here was going to call me on that. I accept the correction.
Maybe this analogy is helpful: saying "qualia" isn't giving us insight into consciousness any more than saying "phlogiston" is giving us insight into combustion. However, that doesn't mean that qualia don't exist or that any reference to them is nonsensical. Phlogiston exists. However, in our better state of knowledge, we've discarded the term and now we call it "hydrocarbons".
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.
Can you state what that version is? Whatever it is, it's nothing I subscribe to, and I call myself a physicalist.
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.
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.
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.
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.
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.