Citation
Israel, D. J. The Role(s) of Logic in Artificial Intelligencein The Handbook of Logic in Artificial Intelligence and Logic Programming, Volume I, Oxford University Press, 1993.
Introduction
From the very beginnings of research in Artificial Intelligence (AI), logic has played a central role. Rather, it has played a number of important roles. More recently, AI has begun to present exciting new challenges and open new lines of inquiry for logic. In this essay, we shall briefly sketch some of the roles logic plays in AI; we shall end with some mention of these recent challenges and lines of inquiry. This essay is not meant as a survey; the Handbook as a whole serves that purpose admirably; as, for each area covered, does each of its parts. Nor is it an editorial introduction to this volume or to the Handbook as a whole; there will, of course, be pointers into the Handbook where relevant. There are many aspects of the relation between work in logic and research in AI that we shall not discuss here.
Most of these are dealt with extensively in the Handbook, many more than once. Finally, we will not provide here an introduction to logic, via an elementary treatment of first order logic. That job has been performed very able in ??.
We shall focus on two very broad roles that logic has played in AI:
(i) as a source of languages and logics for artificial reasoners;
(ii) most importantly, as a source of analytical tools and techniques; more broadly, as providing the underlying mathematical and conceptual framework within which much AI research is done.
The second and more important role will be a theme throughout this essay. As to the new challenges posed for logic by AI, we shall focus only on one family of challenges: nonmonotonic logic or the logic of defeasible reasoning. First, however, we should say something about reasoning, and something about logic. We need to say something about reasoning, because, whatever the differences between the two fields, Logic and AI share a subject matter. AI is directed toward the design and creation of devices capable of the sorts of intelligent behavior that require valid reasoning. On the conception of Logic we are here advancing, Logic is, centrally, the study of reasoning, in particular the study of the principles of valid reasoning. Thus, reasoning is the subject matter that Logic and Arti cial Intelligence share.
