Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/5/84; site sjuvax.UUCP Path: utzoo!linus!philabs!cmcl2!harvard!bbnccv!bbncca!wanginst!decvax!bellcore!petrus!scherzo!allegra!princeton!astrovax!sjuvax!tmoody From: tmoody@sjuvax.UUCP (T. Moody) Newsgroups: net.philosophy Subject: Machines Message-ID: <2464@sjuvax.UUCP> Date: Mon, 28-Oct-85 07:53:32 EST Article-I.D.: sjuvax.2464 Posted: Mon Oct 28 07:53:32 1985 Date-Received: Sun, 3-Nov-85 10:18:18 EST Distribution: net Organization: St. Joseph's University, Phila. PA. Lines: 76 [] If we are going to spend any time discussing minds and machines, we ought to take the time to reach a consensus on the meaning of "machine". This has already become problematic in the exchange between Michael Ellis and Rich Rosen. Rosen concedes, for "machine", what he has refused to concede for "free will": that the term is inherently vague. Astonishing as it is that he should deny the vagueness of "free will" -- given that *its* meaning has been the subject of dispute for centuries -- he is certainly correct about "machine". Philosophical interest in the definition of "machine" is quite young, though. The trouble is, I think, that the word "machine" is used both literally and metaphorically in philosophical discussions (esp. about the mind). Literally, we all understand that machines are man-made artifacts, devices, tools, and systems. In this literal sense, no living thing is a machine. But this doesn't really help, because what we want to know is whether any living things, or parts of living things are sufficiently *like* machines, in essential respects, to justify the application of the term to them. Are cells, for example, "biological machines"? In order to answer this question, we need to *abstract* from the literal meaning of "machine" -- which clearly does *not* include cells -- a more comprehensive meaning that captures what we think is essential to machinehood. For clarity (well, maybe), I shall refer to machines in the latter sense as "Machines" (upper case "M"). It ought to turn out that while all machines are Machines, not all Machines are machines. Proposed definition 1: A Machine is any deterministic system. That is, its current states are exhaustively determined by its prior states. Proposed definition 2: A Machine is any system whose behavior is Turing-computable. That is, its behavior can be completely specified by some finite Turing Machine algorithm. Now, I *think* these two definitions are coextensive...but I'd like to know what you folks think. Here is my reasoning: If a system is deterministic, its behavior is completely described by laws expressible as mathematical functions. Granting the Church/Turing thesis (anything computable is Turing-computable), these are Turing-computable. Okay. Since quantum mechanics, it is no longer plausible to characterize the universe itself as a Machine. In fact, since quantum mechanical systems are not Machines, we are forced to concede that Machines are statistically emergent entities. A digital computer, for example, is a Machine (also a machine, of course), even though the electronic events that animate it are subject to quantum mechanical indeterminacies. The computer is configured in such a way that these indeterminacies are largely cancelled out, so that at a molar level of description a digital computer is approximately deteministic. Is the human brain like a digital computer in *these* respects? Are *its* indeterminacies approximately cancelled out, making it a statistically emergent Machine? This is, after all, an empirical question. Based on what I have read, the answer is no, but I think it is fair to say that the case is not closed. Note that not many neuroscientists state any position on this question, because they are not primarily interested in these metaphysical problems. Sir John Eccles (who is, interestingly, a strict dualist) argues that the brain amplifies quantum indeterminacies, if anything. Also note that this has nothing to do with the Searle argument. Searle's point is that even if one grants the Machinehood of the brain, that is not sufficient to establish its intentionality. Todd Moody | {allegra|astrovax|bpa|burdvax}!sjuvax!tmoody Philosophy Department | St. Joseph's U. | "I couldn't fail to Philadelphia, PA 19131 | disagree with you less."