Many readers will recall some worthwhile exchanges on causality and motion that I had some time back with physicist Robert Oerter. (You’ll find my contributions to our discussion here, here, and here. Oerter exhibited a lapse in judgment more recently, but we should forgive that.) In a recent post, Oerter comments on James Ross’s argument for the immateriality of the intellect -- an argument Ross put forward in his Journal of Philosophy article “Immaterial Aspects of Thought” and his book Thought and World, and which I have developed and defended at length in my ACPQ article “Kripke, Ross, and the Immaterial Aspects of Thought.” What follows are some remarks on Oerter’s remarks.
Ross’s argument, to simplify greatly, is this: (1) All formal thinking is determinate, but (2) No physical process is determinate, so (3) No formal thinking is a physical process. By “formal thinking” what is meant is thinking that conforms to patterns of the sort familiar from mathematics and logic, such as adding, subtracting, squaring, reasoning via modus ponens or modus tollens, and so forth. Ross offers several considerations in support of premise (1), including arguments to the effect that the premise cannot coherently be denied. For one thing, to defend a rejection of premise (1) will require making use of the very patterns of reasoning the rejecter denies we ever really apply. (For instance, you will have to apply forms of reasoning like modus ponens in an argument to the effect that we never determinately reason according to modus ponens.) For another thing, even to deny premise (1) requires that one determinately grasp precisely the patterns one denies we have a determinate grasp of. (For instance, you have determinately to grasp what modus ponens is in the first place and how it differs from other patterns of reasoning in order to go on to deny that we ever determinately grasp what modus ponens is.)
In defense of premise (2), Ross draws on a number of thought experiments from contemporary analytic philosophy, including Kripke’s “quus” paradox and Quine’s “gavagai” example. I’ve discussed Kripke’s paradox here at the blog, though for the most detailed exposition and defense of this and the other elements of Ross’s argument, you need to read the ACPQ article. But if you haven’t done so, you might find it useful to read at least the earlier post on Kripke before continuing, since I will make reference below to points made therein.
“Determinacy” has nothing to do with “determinism”
Oerter makes two main points, which I will consider in reverse order. Alluding to our earlier exchange about causality, he writes:
I have to say it is exceedingly odd to see Feser defending physical indeterminism here. In our discussions of quantum mechanics and causation he argued strenuously that there is no such thing as physical indeterminism - not even in the case of quantum mechanics (where nearly all physicists accept fundamental indeterminism). So I'm wondering how Feser can square real, physical and logical indeterminism with the principle of causality.
But Oerter is confused here on two counts. First -- and not really relevant to the current subject matter -- in the post Oerter is citing I did not “argue strenuously that there is no such thing as physical indeterminism.” On the contrary, I explicitly denied that defending the principle of causality (which is what I was doing) had anything to do with “determinism” in the sense of the view that all events are necessitated by antecedent events and laws of nature. Oerter is making the mistake, common among physicists who write about philosophy, of conflating “causality” and “determinism.” They are simply not the same thing, certainly not as philosophers, especially Aristotelian philosophers, use the term “causality.” Deterministic causality is at most one notion of causality among others.
But as I say, that isn’t really relevant to the subject at hand, which brings us to Oerter’s second confusion. When contemporary philosophers like Ross, Quine, et al. talk about “determinacy” and “indeterminacy” vis-à-vis the content of thought processes and language, what they are saying simply has nothing to do with the debate over determinism and indeterminism vis-à-vis physical causality. Suppose Mitt Romney said last year “I am determined to win this election!” and someone replied “That’s exceedingly odd -- I thought that Romney, as a Mormon, believed in free will, and now he’s saying that his actions are determined! Maybe he’s a compatibilist?” Obviously such a response would fail to see that “determined” doesn’t mean the same thing in every context. Oerter’s making a similar mistake here.
In fact, Ross, Quine, Kripke, et al. would say that the physical facts are “indeterminate,” in the specific sensethey have in mind, even if it turned out that “determinism” of the causal sort were true. So what sense do they have in mind? Here’s a very simple example to illustrate it. Consider the symbol: Δ It has a number of physical features, such as being black, having three straight sides, having a certain size, etc. Now, what exactly is it that Δ is a symbol of? Does it symbolize triangles in general? Black triangles in particular? A slice of pizza? A triangular UFO? A pyramid? A dunce cap? Your favorite Kate Bush video?
There’s nothing in the physical properties of Δ that entails any of these interpretations, or any other for that matter. The physical properties are “indeterminate” in the sense that they don’t fix one particular meaning rather than another. The same is true of any further symbol we might add to this one. For example, suppose the sequence T-R-I-A-N-G-L-E appeared under Δ. There is nothing in the physical properties of this sequence, any more than in Δ, that entails or fixes one particular meaning rather than another. Its physical properties are perfectly compatible with its signifying triangles themselves, or the word “triangle,” or some weird guy who calls himself “Triangle,” or your favorite trip hop acid jazz, or any number of other things.
What Ross, Kripke, et al. are saying when they say that the physical is indeterminate is that no collection of physical facts, and indeed not even the entirety of physical facts, entails any particular meaning rather than another. That would include all the facts about deterministic causation, if causal determinism turned out to be true. For example, even if it so happened that every single time anyone saw Δ or T-R-I-A-N-G-L-E he were rigidly causally determined to utter “That definitely represents triangles, and not a slice of pizza, or a UFO, or some oddball acid jazz music!” there would be nothing about the physical properties of that sequence of sounds, or of its causal relations to any other collection of sounds, brain states, bodily motions, etc., that would by itself entail that the meaning it has is the one we would naturally tend to associate it with.
It is important to emphasize that there is nothing essentially anti-materialist or anti-physicalist about this claim. Ross is a critic of materialism, but many prominent philosophers who are materialists or physicalists -- Quine, Daniel Dennett, Bernard Williams, Alex Rosenberg, and others -- have taken precisely the same view. They hold that for any collection of physical facts, no matter how large, there is nothing about them that entails one specific meaning rather than another. Not only could a materialist agree with Ross’s premise (2), many materialists do agree with it.
Metaphysical not epistemological
Oerter’s second point is the suggestion that for all Ross has shown, the indeterminacy to which he calls our attention is really only epistemological rather than metaphysical. Take Oerter’s example of a mechanical computing device and the question what function it is computing. While there may not be (Oerter allows) any way to know from the physical facts alone which function it computes, that does not entail that there isn’t a fact of the matter, metaphysically, about which function it is computing. But physicalism is challenged only if we have a metaphysical rather than merely epistemological indeterminacy.
It seems that Oerter has not read my ACPQpaper, wherein I address this sort of objection. In fairness to Oerter, Ross does say things in “Immaterial Aspects of Thought” that give the impression that some of the considerations he adduces have more epistemological than metaphysical significance. (For example, Oerter quotes a passage that makes reference to incompatible predicates that are each “empirically adequate.”) That implication is gone in Ross’s restatement of his argument in Thought and World, and Kripke makes it quite clear that the issue is not an epistemological one.
Oerter supposes that when Ross says that the behavior of a machine is indeterminate vis-à-vis the function it is computing, it is the past behavior of the machine that is in question. And he seems to think that this leaves it open that some future behavior, or even just possible behavior, would in principle determine what function it is computing. The problem is just that our information is limited to the past behavior.
But that is not the problem. For not only is any set of past behaviors consistent with incompatible functions, but any set of future behaviors is consistent with them, and indeed any set of possible behaviors is consistent with them. As Kripke points out, you might think that melting wires or slipping gears count as malfunctions, but relative to an eccentric program they might count as the machine doing exactly what it is supposed to be doing, whereas if the wires failed to melt or the gears failed to slip, that would be (relative to such a program) a malfunction. Either way, the physical properties of the machine won’t tell you, no matter how long its operations continue or could continue. Take the complete list of physical behaviors a given machine does exhibit or could exhibit -- a calculator’s outputs, the words and images on a computer screen, the noises a robot makes, or even a machine sputtering, melting, or emitting smoke and sparks. There are always going to be alternative incompatible programs (even if eccentric ones like a program for computing Kripke’s “quus” function) that the machine’s behavior is consistent with. You could take such-and-such behavior as a malfunction in a machine that was running program A, but it could also -- for all any collection of physical facts could in principle entail -- be a machine that is functioning properly as it runs program B.
Of course, you could ask the programmer himself what the machine is supposed to be doing, but that just reinforces the point that the physical facts about the machine itself can’t tell you. And of course, if the materialist claims that the programmer’s mind is itself just a program running in his brain, then appealing to his claims about what the machine is doing really just kicks the problem back a stage. For now the problem is that we need to know what program his brain is really running, and any possible set of physical behaviors he exhibits -- including his speech behavior, considered just in terms of its physical properties, and including anything going on inside his brain -- is compatible with alternative incompatible programs. Nor will appealing to natural selection help, since for any program we conjecture natural selection has put into us, there is going to be an alternative program with equal survival value, and the biological facts will be indeterminate between them. There will be no reason in principle to hold that it is the one program that natural selection put into us rather than the other. (Again, see the post about Kripke and computationalism cited above.)
Quine, Dennett, Rosenberg, et al. -- who, remember, are not attacking physicalism but rather drawing out the implications of the physicalism they accept -- have made points just like these ones themselves, and thus embrace indeterminacy. The dispute between these physicalists on the one hand, and Ross and myself on the other, is whether they can do this coherently. Ross and I argue that they cannot. But at least they see that indeterminacy is a bullet a consistent physicalist has to bite.
0 nhận xét:
Đăng nhận xét