In some respects I think the position is indicated well in a paper by Michael Wheeler, which tackles the question of whether phenomenal experience is realised, at least in part, outside the brain. One reason I think this attempt is representative is its huge ambition. The general thesis of extension is that it makes sense to regard tools and other bodily extensions – the iPad in my hand now, but also simple notepads, and even sticks – as genuine participating contributors to mental events. This is sort of appealing if we’re talking about things like memory, or calculation, because recording data and doing sums are the kind of thing the iPad does. Even for sensory experience it’s not hard to see how the camera and Skype might reasonably be seen as extended parts of my perceptual apparatus. But phenomenal experience, the actual business of how something feels? Wheeler notes a strong intuition that this, at least, must be internal (here read as ‘neural’), and this surely comes from the feeling that while the activity of a stick or pad looks like the sort of thing that might be relevant to “easy problem” cognition, it’s hard to see what it could contribute to inner experience. Granted, as Wheeler says, we don’t really have any clear idea what the brain is contributing either, so the intuition isn’t necessarily reliable. Nevertheless it seems clear that tackling phenomenal consciousness is particularly ambitious, and well calculated to put the overall idea of extension under stress.
Wheeler actually examines two arguments, both based on experiments. The first, from Noë, relies on sensory substitution. Blind people fitted with apparatus that delivers optical data in tactile form begin to have what seems like visual experience (How do we know they really do? Plenty of scope for argument, but we’ll let that pass.) The argument is that the external apparatus has therefore transformed their phenomenal experience.
Now of course it’s uncontroversial that changing what’s around you changed the content of your experience, and changing the content changes your phenomenal experience. The claim here is that the whole modality has been transformed, and without a parallel transformation in the brain. It’s the last point that seems particularly vulnerable. Apparently the subjects adapt quickly to the new kit, too quickly for substantial ‘neural rewiring’, but what’s substantial in this context? There are always going to be some neural changes during any experience, and who’s to say that those weren’t the crucial ones?
The second argument is due to Kiverstein and Farina, who report that when macaques are trained to use rakes to retrieve food, the rakes are incorporated into their body image (as reflected in neural activity). This is easy enough to identify with – if you use a stick to probe the ground, you quickly start to experience the ‘feel’ of the ground as being at the end of the stick, not in your hand. Does it prove that your phenomenal experience is situated partly in the stick? Only in a sense that isn’t really the one required – we already felt it as being in the hand. We never experience tactile sensation as being in the brain: the anti-extension argument is merely that the brain is uniquely the substrate where it the feeling is generated.
Wheeler, rather anti-climatically but I think correctly, thinks neither argument is successful; and that’s another respect in which I think his paper represents the state of the extended mind thesis; both ambitious and unproven.
Worse than that, though, it illustrates the point which kills things for me; I don’t really care one way or the other. Shall we call these non-neural processes mental? What if we do? Will we thereby get a new insight into how mental processes work? Not really, so why worry? The thesis that experience is external in a deeper sense, external to my mind, is strange and mind-boggling; the thesis that it’s external in the flatly literal sense of having some of its works outside the brain is just not that philosophically interesting.
OK, it’s true that what we know about the brain doesn’t seem to explicate phenomenal experience either, and perhaps doesn’t even look like the kind of thing that in principle might do so. But if there are ever going to be physical clues, that’s kind of where you’d bet on them being.
Is phenomenal experience extended? Well, I reckon phenomenal experience is tied to the non-phenomenal variety. Red qualia come with the objective perception of red. So if we accept the extended mind for the latter, we should probably accept it for the former. But please yourself; in the absence of any additional illumination, who cares where it is?