Bats  10 May 2004
Who knows?  Nagel's classic "What is it like to be a bat?"must be one of the most influential papers on consciousness of the last century, and it's still very relevant. Nagel's aim is to launch a kind of counter-attack against physicalist arguments, which would reduce the mental to the merely physical, and which were evidently getting into the ascendant in 1974 when the paper was published. Tempting as it may be to fall back on the familiar kind of reductionist approach which has worked so well in other areas, Nagel argues, phenomenal, subjective experience is a special case. Reductive arguments always seek to give an explanation in objective terms, but the essential point about conscious experiences is that they are subjective. The whole idea of an objective account therefore makes no sense - no more sense than asking what my inward experiences are really like, as opposed to how they seem to me. How they seem to me is all there is to them. Any neutral, objective, third-person explanation has to leave out the essence of the experience. The point about conscious experience is that there is something it is like to see x, or hear y, or feel z.
Ah, 'there is something it is like' - the phrase that launched a thousand papers. Surely you realise that this is just an over-literal interpretation of the conventional phrase 'what is it like?'. To assume that the 'it' in that question represents a real thing rather than a grammatical quirk is just silly.
Yes, I understand your point, but Nagel's  whole point is that 'what it's like' is strictly inexpressible in objective terms. So it isn't surprising that he has to resort to a back-handed way of getting you to see what he's talking about. If he could describe it straightforwardly, he'd be contradicting his own theory. Anyway. Nagel uses the example of a bat to dramatise his case - how can we know what it is like to be a bat, from the inside?
There's a large rhetorical element in the choice of a bat. Bats have the traditional reputation of being a bit weird, and it's known that some of them have a sense we don't - echolocation. All this helps to persuade people that we can't imagine what things are like from another point of view. But if Nagel is right, it should be equally hard to see things from the point of view of an identical twin. So let's get the bats out of this particular belfry, OK?
Nagel's entitled to use any example he likes. He explains that he chose bats because they're close enough to human beings to leave most people in no doubt that they have conscious experiences of some kind, while far enough from us to dramatise his case. But whether you like it or not, it raises some fundamental issues. If Nagel is right, there are certain experiences - bat experiences, for example - that humans can never have. It follows that there are true facts about these experiences which humans can never grasp (although they can grasp that there must be facts of this kind. This general conclusion about the limits of human understanding must have been part of the inspiration for Colin McGinn's wider theory that even human consciousness is ultimately beyond our understanding.
Yes, of course, since human beings are by definition not bats, they can't have the experience of being a bat. But it does not follow that there are facts about bat experiences they can't understand. You see, actually we can know what it's like to be a bat. We can know what sizes of objects echolocation detects, and how the bat directs its ears and the stream of sound, and thousands of facts of that kind. We can know all about the kinds of information a bat's senses supply, and with the right equipment we can experience echolocation ourselves at least by proxy. I think the worst part of the paper is where Nagel says that even if we imagine ourselves turning into a bat, that won't be any good. We're just imagining what it would be like for us to be a bat, whereas we need to imagine what it's like for a bat. This just reduces the whole thing to the trivial point that we can't stop being us. Because if we did - it wouldn't be us any more!
You just need to make the imaginative effort to see what he's on about. Actually, the claim being made is quite modest in some respects. Nagel himself says that his argument doesn't disprove physicalism. It would be nearer the truth to say that physicalism, the view that mental entities are physical entities, is a hypothesis we can't even understand properly...