Two conditional logics for defeasible inference: A comparison preliminary version

Abstract

We compare two conditional logics for defeasible inference: Alchourrón's defeasible logic DFT and Boutilier's CO logic. The two logics share the distinguishable characteristics common to most logics for defeasible inference. Namely, their conditional connective defeat the rules of Modus Ponens, Strengthening the Antecedent, Transitivity, and Contraposition. Although both logics have possible worlds semantics, Boutilier's is relational while Alchourrón's is non-relational. In this note we reveal the connection between the two, concluding that the conditional sentences validated by both logics are precisely the same.