Blogosophy

Motion Induced Blindness

Very cool Motion Induced Blindness optical illusion. As I've said before, about the checkerboard illusion, I think this kind of thing really undermines the plausibility argument for "zombies" (creatures indistinguishable from humans, but who lack qualia)--and plausibility is the only argument there is that it's a coherent notion. We think that we can imagine seeing the color red but having a completely different (in some hard-to-specify sense) feeling of what it's like to see red than someone else who also sees that color and tells us "yep, that's red." From this the argument goes that it's conceivable that someone could say "that's red" whenever we would, but who has nothing that it feels like to see red; there's just a bunch of nerves firing and chemicals changing, but nothing subjective going on. And if it's conceivable, so it is said, then it's possible.
I think, though, that it's harder (maybe even impossible) to imagine a zombie being fooled by this optical illusion; the illusion is, after all, precisely that you're losing the sense of what it is to feel like you're seeing one or more of the yellow dots, even though physically the photons are still hitting your eyes, the nerves are firing, etc. The lights are on, but you're intermittently not home to Mr. Yellow-dot Qualia. Is it conceivable that the zombie sees but isn't really aware of seeing the yellow dot, and also sees but isn't really aware of not seeing the yellow dot, and yet somehow still can distinguish objectively between the two states (so it can describe the illusion) just like someone with a mind? Or does your brain seize up in a kind of concept induced blindness trying to picture it?

Brian Weatherson points to David Chalmers's _Does Conceivability Entail Possibility paper, and comments on it, but unfortunately Brown.edu is down at the moment so I can't get the right archive link going. Wo also has a post on Conceivability, Possibility, and Zombies. Both Brian and wo take a much more analytical approach, trying to tease out whether it's possible to construct a simple logical statement that clearly shows a conceivable but impossible world; I'm just trying to undermine the plausibility of the intuition that because we think we can imagine having the qualia of green while seeing red, and vice-versa, with no way of verifying this against others's sensations, it makes sense to suppose seeing red (and being able to act appropriately as if one had seen red) accompanied by no qualia whatsoever.

Tip of the hat to The Volokh Conspiracy for the link to the illusion.