Again, yesterday’s post is probably required pre-reading. I apologize for the scattered nature of these posts, but as you probably have guessed I am writing a paper (for publication) on Kylie’s puzzle and its implications for the connection between content externalism and consciousness, and so these posts reflect more the order in which I develop my ideas than the order of the overall argument, unlike my normal posts which are normally short enough to allow me to sort everything out in one day.
Some have argued that Kylie’s puzzle can be solved by uncovering something amiss about the sense in which Kylie knows something about the external world (Hohwy, J. (2002). Privileged Self-Knowledge and Externalism: A Contextualist Approach. Pacific Philosophical Quarterly 83 (3), 235–252) or the sense in which that knowledge is a priori (Miller, R. W. (1997). Externalist Self-Knowledge and the Scope of the A Priori. Analysis 57 (1), 67–75, but see Brueckner, A. (2000). Externalism and the A Prioricity of Self-Knowledge. Analysis 60 (265), 132–136 for a rebuttal). But such solutions, even if valid, fail to resolve the problem that is at the core of the puzzle, which is that content externalism seems to put too much into consciousness. For example, we can modify the puzzle to involve a twin earth type situation, by assuming that Kylie is secretly transported to twin earth at some point, and that this happens before scientists have discovered what water is composed of. Before the switch if Kylie had reflected upon the experience of thinking about water she would have concluded that water-H2O exists, but after the switch she will conclude that water-XYZ exists. This would imply that Kylie can detect that she has been transported to twin earth, by noticing that there is a difference in what she is motivated to conclude exists by such reasoning. But, assuming that she has been switched with her twin earth duplicate, this is absurd, because Kylie’s behavior will be the same as if she hadn’t been transported to twin earth. And that means that normal people who are not switched to twin earth will often falsely conclude that they have been (as Kylie, were she to not have been switched, would have), and announce that fact to the world, or that people who realize that they have been transported to twin earth never announce that fact, or alter their behavior in any way on the basis of it. Like the puzzle in its original form this implies that we must either reject privileged access or content externalism, and this time whether Kylie really knows that water-H2O exists, or if that knowledge is really a priori, is irrelevant.
Now not every philosopher is convinced by inverted earth type arguments, and the inverted earth scenario by itself may seem to motivate giving up the idea that qualia depend on anything external (and so it may seem like overkill to invoke it just to rule out a single possible response). And there is serious debate about whether the inverted earth argument is successful. But I think appealing to it here is justified, regardless of its implications for qualia by itself (or lack thereof), because here we are interested not just in qualia, but in our privileged access to them. So what does privileged access entail? Well privileged access implies, at the very minimum, that when we think about our qualia we can’t be wrong, that if I sincerely think that I am in pain then I am in fact in pain. But the existence of privileged access must do more than guarantee that our conscious reflections on our qualia aren’t in error, it must ensure that our qualia make a causal difference. If it didn’t then we could very well be skeptics about being conscious, after all we can’t just appeal to conscious experience in order to justify that we have conscious experience (not without begging the question), our conscious experience needs to make a difference, so that we can point to its effects and use them to justify our very strong intuition that we are in fact conscious. And such skepticism is the very bullet we are trying to avoid biting. This brings us back to inverted earth. In this context the inverted earth thought experiment shows that a change in qualia, so understood, doesn’t necessarily have a causal effect. And this implies that we can rationally doubt that we have such qualia, or, at the very least, that they are distinct from each other. If my experience of green could be replaced with an experience of red without it making any causal difference then how can I know that I ever experience green? Maybe I only think, mistakenly, that there is a phenomenal distinction between red and green when really there is only a causal difference between red and green stimuli. So, given that we are committed to trying to avoid biting the bullet and accepting that we don’t have privileged access to our own qualia, we can safely appeal to the inverted earth thought experiment in this context.