"A computer program capable of acting intelligently in the world must have a general representation of the world in terms of which its inputs are interpreted. Designing such a program requires commitments about what knowledge is and how it is obtained. Thus, some of the major traditional problems of philosophy arise in artificial intelligence.More specifically, we want a computer program that decides what to do by inferring in a formal language that a certain strategy will achieve its assigned goal. This requires formalizing concepts of causality, ability, and knowledge. Such formalisms are also considered in philosophical logic." - from the Introduction Reprinted in Matthew Ginsberg (ed.), Readings in Nonmonotonic Reasoning, pp. 26{45, San Francisco: Morgan Kaufmann Publishers, Inc., 1987

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