- Searle is certainly right that instantiating the same program that the brain does is not, in and of itself, a sufficient condition for having those propositional attitudes characteristic of the organism that has the brain. If some people in AI think that it is, they're wrong. As for the Turing test, it has all the usual difficulties with predictions of "no difference"; you can't distinguish the truth of the prediction from the insensitivity of the test instrument1.
- However, Searle's treatment of the "robot reply" is quite unconvincing. Given that there are the right kinds of causal linkages between the symbols that the device manipulates and things in the world - including the afferent and efferent transducers of the device - it is quite unclear that intuition rejects ascribing propositional attitudes to it. All that Searle's example shows is that the kind of causal linkage he imagines - one that is, in effect, mediated by a man sitting in the head of a robot - is, unsurprisingly, not the right kind.
- We don't know how to say what the right kinds of causal linkage are. This, also, is unsurprising since we don't know how to answer the closely related question as to what kinds of connection between a formula and the world determine the interpretation under which the formula is employed. We don't have an answer to this question for any symbolic system; a fortiori, not for mental representations. These questions are closely related because, given the mental representation view, it is natural to assume that what makes mental states intentional is primarily that they involve relations to semantically interpreted mental objects; again, relations of the right kind.
- It seems to me that Searle has misunderstood the main point about the treatment of intentionality in representational theories of the mind; this is not surprising since proponents of the theory - especially in AI - have been notably unlucid in expounding it. For the record, then, the main point is this: intentional properties of propositional attitudes are viewed as inherited from semantic properties of mental representations (and not from the functional role of mental representations, unless "functional role" is construed broadly enough to include symbol-world relations). In effect, what is proposed is a reduction of the problem what makes mental states intentional to the problem what bestows semantic properties on (fixes the interpretation of) a symbol. This reduction looks promising because we're going to have to answer the latter question anyhow (for example, in constructing theories of natural languages); and we need the notion of mental representation anyhow (for example, to provide appropriate domains for mental processes). It may be worth adding that there is nothing new about this strategy. Locke, for example, thought (a) that the intentional properties of mental states are inherited from the semantic (referential) properties of mental representations; (b) that mental processes are formal (associative); and (c) that the objects from which mental states inherit their intentionality are the same ones over which mental processes are defined: namely ideas. It's my view that no serious alternative to this treatment of propositional attitudes has ever been proposed.
- To say that a computer (or a brain) performs formal operations on symbols is not the same thing as saying that it performs operations on formal (in the sense of "uninterpreted") symbols. This equivocation occurs repeatedly in Searle's paper, and causes considerable confusion. If there are mental representations they must, of course, be interpreted objects; it is because they are interpreted objects that mental states are intentional. But the brain might be a computer for all that.
- This situation - needing a notion of causal connection, but not knowing which notion of causal connection is the right one - is entirely familiar in philosophy. It is, for example, extremely plausible that "a perceives b" can be true only where there is the right kind of causal connection between a and b. And we don't know what the right kind of causal connection is here either. Demonstrating that some kinds of causal connection are the wrong kinds would not, of course, prejudice the claim. For example, suppose we interpolated a little man between a and b, whose function it is to report to a on the presence of b. We would then have (inter alia) a sort of causal link from a to b, but we wouldn't have the sort of causal link that is required for a to perceive b. It would, of course, be a fallacy to argue from the fact that this causal linkage fails to reconstruct perception to the conclusion that no causal linkage would succeed. Searle's argument against the "robot reply" is a fallacy of precisely that sort.
- It is entirely reasonable (indeed it must be true) that the right kind of causal relation is the kind that holds between our brains and our transducer mechanisms (on the one hand) and between our brains and distal objects (on the other). It would not begin to follow that only our brains can bear such relations to transducers and distal objects; and it would also not follow that being the same sort of thing our brain is (in any biochemical sense of "same sort") is a necessary condition for being in that relation; and it would also not follow that formal manipulations of symbols are not among the links in such causal chains. And, even if our brains are the only sorts of things that can be in that relation, the fact that they are might quite possibly be of no particular interest; that would depend on why it's true2. Searle gives no clue as to why he thinks the biochemistry is important for intentionality and, prima facie, the idea that what counts is how the organism is connected to the world seems far more plausible. After all, it's easy enough to imagine, in a rough and ready sort of way, how the fact that my thought is causally connected to a tree might bear on its being a thought about a tree. But it's hard to imagine how the fact that (to put it crudely) my thought is made out of hydrocarbons could matter, except on the unlikely hypothesis that only hydrocarbons can be causally connected to trees in the way that brains are.
- The empirical evidence for believing that "manipulation of symbols" is involved in mental processes derives largely from the considerable success of work in linguistics, psychology, and AI that has been grounded in that assumption. Little of the relevant data concerns the simulation of behavior or the passing of Turing tests, though Searle writes as though all of it does. Searle gives no indication at allot how the facts that this work accounts for are to be explained if not on the mental-processes-are-formal-processes view. To claim that there is no argument that symbol manipulation is necessary for mental processing while systematically ignoring all the evidence that has been alleged in favor of the claim strikes me as an extremely curious strategy on Searle's part.
- Some necessary conditions are more interesting than others. While connections to the world and symbol manipulations are both presumably necessary for intentional processes, there is no reason (so far) to believe that the former provide a theoretical domain for a science; whereas, there is considerable a posteriori reason to suppose that the latter do. If this is right, it provides some justification for AI practice, if not for AI rhetoric.
- Talking involves performing certain formal operations on symbols: stringing words together. Yet, not everything that can string words together can talk. It does not follow from these banal observations that what we utter are uninterpreted sounds, or that we don't understand what we say, or that whoever talks talks nonsense, or that only hydrocarbons can assert - similarly, mutatis mutandis, if you substitute "thinking" for "talking."
- I assume, for simplicity, that there is only one program that the brain instantiates (which, of course, there isn't). Notice, by the way, that even passing the Turing test requires doing more than just manipulating symbols. A device that can't run a typewriter can't play the game.
- For example, it might be that, in point of physical fact, only things that have the same simultaneous values of weight, density, and shade of gray that brains have can do the things that brains can. This would be surprising, but it's hard to see why a psychologist should care much. Not even if it turned out - still in point of physical fact - that brains are the only things that can have that weight, density, and color. If that's dualism, I imagine we can live with it.
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