"Wait, what? Searle claims that functionalists are dualists? And that therefore they must claim not to be? This makes no sense."He claims that they, as monists, are inheriting the dualist categories and arguing that one of them doesn't exist. He thinks the sane approach to reconciling the body and the mind is to reject that categorization.
So for example Searle has talked about the problem of how we can get real free will in the sense that we feel there were other options open to us, and we responsibly decided upon the one option. Modern functionalists try to create something which is functionally indistinguishable -- so, for example, a computer which 'sorta decides' which path to take based on a random number generator and a trainable probability distribution.
On this account the feeling that other options are open is more or less some sort of conscious illusion -- we feel like there are many options open to us, but if we really understood what was going on down in the plumbing, we would say "aha, I was deterministic all the way." The remaining loose end is shored up with an appeal to compatibilism: "this is perfectly consistent with free will, because 'free will' should just name my internal logic which determined my action -- and we've got that if our training model and probability distribution is complicated enough."
Searle in Liberty and Neurobiology says that this is indeed one option which he can't really impeach: it's possible that our very feeling that we have 'other options open' is somehow an utter and complete illusion generated in our conscious experience to make us feel relevant, when really there is a brute mechanical process which takes us through our everyday lives.
Notice that it has to be an illusion to Searle, because he is not willing to take the implicit step which functionalists necessarily make in looking for something "functionally indistinguishable": the functionalist ignores the touchy-feely intuitions which people have. Functionalists don't want to talk about the conscious aspects of consciousness, because their inheriting a materialism which is historically contra Cartesian dualism. You see it right in the Dennett article: who does he try to lump Penrose and Searle with? Renee Descartes.
Searle's approach instead says something like, "Consciousness is a real feature of real material structures in the real world and we're not going to explain it if our theories just ignore it. Fortunately, its philosophical status is not too complicated and we can solve this problem, leaving the hard scientific puzzle to the scientists."
"If I write a program that computes the first N squares, and you don't understand the symbols, the computation has nevertheless happened. The claim that Turing computation is observer-relative is equivalent to claiming that if I don't know how x86 works, then my computer won't boot. Of course it will (and likewise, of course, whatever perspective you switch to has no effect on my consciousness)."
Well, no, those aren't equivalent. The symbols which appear on your computer screen are in fact interpreted by you as meaningful, regardless of what you think about the instruction set, and that is the reason that the thing is a computer for you. You are right, you do not need to interpret the x86 code directly to interpret the results of the computation -- nonetheless you do need to interpret the computer as a computation.
So that's a bit abstract. Just think of what would happen if I modified your OS (more precisely, I suppose, the display server) so that, right before the image gets sent to the screen, it gets encrypted under AES in CMC mode. So you boot up your computer and suddenly the screen just fills with what looks like random pixel noise, you move your mouse and suddenly the whole screen changes to other noise.
Is it still functional as a computer? You might defend the idea that "yes, even though it's totally unusable now for any computation, it's still computing all the things it used to compute." Searle wants to say that if you accept this, then trivially everything is a computer and the claim that the brain is a computer is a vacuous claim. Why? Because imagine something which you would not normally mistake for a computer: throwing a baseball around with your kid. Strictly speaking, there is an 'intrinsic computation' of this sort which the ball is doing -- it is computing parabolas, complete with an all-order perturbation theory calculation of the effects of wind resistance, spin, wind, pressure noise, etc.
Searle wants to say: that ball doesn't become a computer until you start using it to compute those things. And that's a perspective shift which you need to make. Perhaps to create an effective android to throw baseballs to your kid, you should model all of this in detail. Perhaps that android can then help us to understand what happens to the baseball. Searle doesn't have a problem with either of those. But if the baseball is just intrinsically a computer then it's hard to find something which isn't, from some perspective, a computer. Every particle in the visible universe -- as well as perhaps every subset of particles in the universe -- would seem to be computing something "in principle".
And if we return to the computing-the-squares puzzle -- how do you know that it computed the sequence of squares, and not, say, the odd numbers? Just like my invertible transform of your screen into random data, there is an invertible transform from the squares to the odd numbers -- especially if you store a 'sequence' as a list of differences between its elements, in which case the sequence of squares is in fact stored as the list (1 3 5 7 9 11 ...) . How do you know that you didn't compute the Fibonacci numbers, given that there is a bijection from the squares to the Fibonacci numbers?
In contrast, if I seal you in a box so that you can't communicate with the world, you are still able to feel things. As an asymmetry with computers, if I say that you really are conscious in this sense, it does not immediately imply that every particle and aggregation of particles in the universe is conscious.