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Mental Objects/AI Research/Norvig/Russell: Mental objects have been the subject of intensive study in philosophy and AI. There are three main approaches.
A. The one taken in this chapter, based on modal logic and possible worlds, is the classical approach from philosophy (Hintikka, 1962(1); Kripke, 1963(2); Hughes and Cresswell, 1996(3)). The book Reasoning about Knowledge (Fagin et al., 1995)(4) provides a thorough introduction.
B. The second approach is a first-order theory in which mental objects are fluents. Davis (2005)(5) and Davis and Morgenstern (2005)(6) describe this approach. It relies on the possible-worlds formalism, and builds on work by Robert Moore (1980(7), 1985(8)).
C. The third approach is a syntactic theory, in which mental objects are represented by character
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strings. A string is just a complex term denoting a list of symbols, so CanFly(Clark) can be represented by the list of symbols [C, a, n,F, l, y, (,C, l, a, r, k, )]. The syntactic theory of mental objects was first studied in depth by Kaplan and Montague (1960)(9), who showed that it led to paradoxes if not handled carefully. Ernie Davis (1990)(10) provides an excellent comparison of the syntactic and modal theories of knowledge.
1. Hintikka, J. (1962). Knowledge and Belief. Cornell University Press.
2. Kripke, S. A. (1963). Semantical considerations on modal logic. Acta Philosophica Fennica, 16, 83-94.
3. Hughes, G. E. and Cresswell, M. J. (1996). A New Introduction to Modal Logic. Routledge
4. Fagin, R., Halpern, J.Y.,Moses,Y., and Vardi,M.Y. (1995). Reasoning about Knowledge. MIT Press.
5. Davis, E. (2005). Knowledge and communication: A first-order theory. AIJ, 166, 81–140.
6. Davis, E. and Morgenstern, L. (2005). A first-order theory of communication and multi-agent plans. J. Logic and Computation, 15(5), 701–749.
7. Moore, R. C. (1980). Reasoning about knowledge and action. Artificial intelligence center technical note 191, SRI International.
8. Moore, R. C. (1985). A formal theory of knowledge and action. In Hobbs, J. R. and Moore, R. C.
(Eds.), Formal Theories of the Commonsense World, pp. 319–358. Ablex.
9. Kaplan, D. and Montague, R. (1960). A paradox regained. Notre Dame Journal of Formal Logic, 1(3),
10. Davis, E. (1990). Representations of Commonsense Knowledge. Morgan Kaufmann._____________Explanation of symbols: Roman numerals indicate the source, arabic numerals indicate the page number. The corresponding books are indicated on the right hand side. ((s)…): Comment by the sender of the contribution. The note [Author1]Vs[Author2] or [Author]Vs[term] is an addition from the Dictionary of Arguments. If a German edition is specified, the page numbers refer to this edition.
Stuart J. Russell
Artificial Intelligence: A Modern Approach Upper Saddle River, NJ 2010