From owner-cse575-fa07-list@LISTSERV.BUFFALO.EDU Thu Aug 30 20:15:39 2007 Date: Thu, 30 Aug 2007 20:15:25 -0400 From: "William J. Rapaport" Subject: Further thoughts on the nature of cognitive science To: CSE575-FA07-LIST@LISTSERV.BUFFALO.EDU ------------------------------------------------------------------------ Subject: Further thoughts on the nature of cognitive science ------------------------------------------------------------------------ In my efforts not to get too far behind the syllabus at this early stage of the course, there are some things I want to bring to your attention but that I don't want to spend class time on (unless they come up again later on, which some of them might). So I'll discuss such things on the Listserv. Please feel free to ask questions about them in class or on the Listserv. This time, I'd like to present 3 major ideas underlying (computational) cognitive science. (I hinted at some of them in lecture today.) 1. Newell & Simon's Physical Symbol System Hypothesis 2. The representational theory of mind & Fodor's language of thought 3. Dennett's theory of the intentional stance 1. Newell & Simon's Physical Symbol System Hypothesis ------------------------------------------------------------------------ Allen Newell & Herbert Simon were two of the pioneers of AI and of cognitive science (Simon won the Nobel prize in economics.) In their 1976 paper, "Computer Science as Empirical Inquiry", http://www.cse.buffalo.edu/~rapaport/575/F07/cgsmiscrdgs.html#newellsimon76 they proposed the "Physical Symbol System Hypothesis": A physical system can *exhibit intelligent behavior* iff it is a physical *symbol system*. A "symbol system" is essentially a Turing machine, i.e., a mathematical model of computation. And a "physical" symbol system is a physical implementation of a symbol system, i.e., a computer. 2. The representational theory of mind (RTM) & Fodor's language of thought (LOT) ------------------------------------------------------------------------ The RTM (or the CRUM--computational representational understanding of mind--as, I think, Thagard calls it :-) says: Mental processes are computations (or "rules") that operate on symbols that are mental representations (of things in the world). The philosopher Jerry Fodor's LOT hypothesis is: Mental representations are a language, with a syntax (i.e., a grammar) (and *maybe* with a semantics). You can read more about these in our texts (in particular Cummins Ch.4), in MITECS, and in Fodor's book, The Language of Thought: http://www.cse.buffalo.edu/~rapaport/575/F07/cgsmiscrdgs.html#fodor75 The reason I think that Fodor's LOT might not come with a semantics is because of Fodor's related theory of "methodological solipsism", essentially the view that the proper study of the mind does *not* need to pay any attention to the way the world is, roughly because everything that the mind believes about the world has first been "internalized"; see his 1980 paper, "Methodological Solipsism Considered as a Research Strategy in Cognitive Psychology": http://www.cse.buffalo.edu/~rapaport/575/F07/cgsmiscrdgs.html#fodor80 3. Dennett's theory of the intentional stance ------------------------------------------------------------------------ In his 1971 article, "Intentional Systems", http://www.cse.buffalo.edu/~rapaport/575/F07/cgsmiscrdgs.html#dennett71 the philosopher Daniel C. Dennett argued that it makes sense to treat certain complex systems *as if* they had beliefs and other "intentional" states, even if they don't. (By "intentional", Dennett merely means "mental"; this is a term of art in philosophy that I'll write about in another message.) There is a sort of hierarchy of "stances" that one can take towards such a complex system: a) The physical stance, in which you explain and predict the system's behavior in terms of its physical implementation: This is best for explaining and predicting malfunctions. E.g., you could say that a chess-playing computer crashed because transistor #7 misfired (or something like that). b) The design stance, in which you explain and predict the system's behavior in terms of its design. In the case of a computer program (which, by the way, is what Simon believes is the prime example of a complex system), this would be its program. E.g., you could say that a chess-playing computer castled because of a certain IF statement on line 7 of its program. c) The intentional stance, in which you explain and predict the system's behavior by treating it like an intelligent entity, i.e., in terms of beliefs, desires, and intentions. E.g., you might say that the chess-playing computer castled because it believed that that was the best response to its opponent's Armenian defense (or whatever). When Kasparov lost to Deep Blue, he described his computer opponent in intentional terms!