Production and Causal Logics for Nonmonotonic Reasoning Alexander Bochman Computer Science Department, Holon Academic Institute of Technology, Israel Abstract We introduce logical formalisms of production and causal inference relations based on input/output logics of [Makinson and van der Torre, 2000]. These inference relations are assigned, however, both standard monotonic semantics, and natural nonmonotonic semantics based on the principle of explanatory closure. The resulting nonmonotonic for- malisms will be shown to provide a logical representation of abductive reasoning, and a complete characterization of causal nonmonotonic reasoning from [McCain and Turner, 1997]. The results of the study suggest production and causal inference as a new general framework for nonmonotonic reasoning. 1 Introduction The field of nonmonotonic reasoning is so abundant with different formalisms, that an attempt to introduce and justify yet another one appears to be doomed from the very beginning. Nevertheless, this is precisely the main aim of this study. Accordingly, we have to explain, first of all, what was the problem such that the new formalism is the suggested solution. To begin with, studies in nonmonotonic reasoning have given rise to two basically different approaches that could be called, respectively, preferen- tial and explanatory nonmonotonic reasoning, with little interaction between them 1 . The first approach encompasses nonmonotonic inference relations of 1 They have been called, respectively, classical and argumentative nonmonotonic rea- soning in [Bochman, 2001]. 1