The CT thesis would seem to imply the possibility of strong AI. That is, it implies that: On any general-purpose computer, there is some computer program that (if supplied with enough memory, e.g. a huge disk drive) can display the exact same behaviors as a human, but perhaps on a much slower time-scale.
It doesn't imply that strong AI can be achieved by any means other than direct human-imitation, and it doesn't say anything about how fast a computer has to be or how big it has to be to display a given functionality. It also is just a philosophical hypothesis, not something that has been scientifically proved.... Although, one can argue for it on physics grounds, as some have done, and as David Deutsch has done for the related Quantum Church-Turing Thesis. -- Ben G > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On > Behalf Of Anand AI > Sent: Tuesday, January 14, 2003 2:29 PM > To: AGI List > Subject: [agi] C-T Thesis (or a version thereof) - Is it useable as an > in-principle argument for strong AI? > > > Hi everyone, > > After having read quite a bit about the the C-T Thesis, and its different > versions, I'm still somewhat confused on whether it's useable as an > in-principle argument for strong AI. Why or why isn't it > useable? Since I > suspect this is a common question, any good references that you have are > appreciated. (Incidentally, I've read Copeland's entry on the > C-T Thesis in > SEoC (plato.standford.edu).) > > I'll edit any answers for SL4's Wiki > (http://sl4.org/bin/wiki.pl?HomePage), > and thanks very much in advance. > > Best wishes, > > Anand > _______________________________________________ > > The following text is from the MIT Encyclopedia of Cognitive Sciences: > > COMPUTATION AND THE BRAIN > > Two very different insights motivate characterizing the brain as > a computer. > The first and more fundamental assumes that the defining function > of nervous > systems is representational; that is, brain states represent > states of some > other system the outside world or the body itself-where > transitions between > states can be explained as computational operations on > representations. The > second insight derives from a domain of mathematical theory that defines > computability in a highly abstract sense. > > The mathematical approach is based on the idea of a Turing machine. Not an > actual machine, the Turing machine is a conceptual way of saying that any > well-defined function could be executed, step by step, according to simple > "if you are in state P and have input Q then do R" rules, given > enough time > (maybe infinite time; see COMPUTATION). Insofar as the brain is a device > whose input and output can be characterized in terms of some mathematical > function- however complicated -then in that very abstract sense, it can be > mimicked by a Turing machine. Because neurobiological data indicate that > brains are indeed cause-effect machines, brains are, in this formal sense, > equivalent to a Turing machine (see CHURCHTURING THESIS). > Significant though > this result is mathematically, it reveals nothing specific about > the nature > of mindbrain representation and computation. It does not even > imply that the > best explanation of brain function will actually be in > computational/representational terms. For in this abstract sense, livers, > stomachs, and brains-not to mention sieves and the solar > system-all compute. > What is believed to make brains unique, however, is their evolved capacity > to represent the brain's body and its world, and by virtue of computation, > to produce coherent, adaptive motor behavior in real time. > > CHURCH-TURING THESIS > > Alonzo Church proposed at a meeting of the American Mathematical > Society in > April 1935, "that the notion of an effectively calculable function of > positive integers should be identified with that of a recursive function." > This proposal of identifying an informal notion, effectively calculable > function, with a mathematically precise one, recursive function, has been > called Church's thesis since Stephen Cole Kleene used that name in 1952. > Alan TURING independently made a related proposal in 1936, > Turing's thesis, > suggesting the identification of effectively calculable functions with > functions whose values can be computed by a particular idealized computing > device, a Turing machine. As the two mathematical notions are provably > equivalent, the theses are "equivalent," and are jointly referred > to as the > Church-Turing thesis. > > The reflective, partly philosophical and partly mathematical, work around > and in support of the thesis concerns one of the fundamental notions of > mathematical logic. Its proper understanding is crucial for > making informed > and reasoned judgments on the significance of limitative > results-like G�DEL' > S THEOREMS or Church's theorem. The work is equally crucial for computer > science, artificial intelligence, and cognitive psychology as it provides > also for these subjects a basic theoretical notion. For example, > the thesis > is the cornerstone for Allen NEWELL's delimitation of the class > of physical > symbol systems, that is, universal machines with a particular > architecture. > Newell (1980) views this delimitation "as the most fundamental > contribution > of artificial intelligence and computer science to the joint enterprise of > cognitive science." In a turn that had almost been taken by Turing (1948, > 1950), Newell points to the basic role physical symbol systems have in the > study of the human mind: "the hypothesis is that humans are instances of > physical symbol systems, and, by virtue of this, mind enters into the > physical universe . . . this hypothesis sets the terms on which we search > for a scientific theory of mind." The restrictive "almost" in > Turing's case > is easily motivated: he viewed the precise mathematical notion as > a crucial > ingredient for the investigation of the mind (using computing machines to > simulate aspects of the mind), but did not subscribe to a sweeping > "mechanist" theory. It is precisely for an understanding of such-sometimes > controversial-claims that the background for Church's and > Turing's work has > to be presented carefully. Detailed connections to investigations in > cognitive science, programmatically indicated above, are at the heart of > many contributions (cf. for example, COGNITIVE MODELING, COMPUTATIONAL > LEARNING THEORY, and COMPUTATIONAL THEORY OF MIND). > > ------- > To unsubscribe, change your address, or temporarily deactivate > your subscription, > please go to http://v2.listbox.com/member/?[EMAIL PROTECTED] > ------- To unsubscribe, change your address, or temporarily deactivate your subscription, please go to http://v2.listbox.com/member/?[EMAIL PROTECTED]
