Abstract

MARANHAO, Juliano S. A.. Why was Alchourrón afraid of snakes?. Anal. filos. [online]. 2006, vol.26, n.1, pp.62-92. ISSN 1851-9636.

In the last papers published by Alchourrón, he attacked non-monotonic logics, which he considered philosophically unsound for the representation of defeasible reasoning. Instead of a non-monotonic consequence relation, he proposed a formal representation of defeasibility based on an AGM-like revision of implicit assumptions connected to the premises. Given that this is a procedure to generate non-monotonic logics, it is not clear, from a mathematical standpoint, why he was so suspicious of such logics. In the present paper we try to answer this question based on Alchourrón' s convictions about epistemology, particularly the epistemology of law. We also propose another revision operator on theories called refinement, which provides a faithful representation of the sort of epistemic change considered by Alchourrón as intrinsic to defeasibility.

Keywords : Defeasibility; Non-monotonic logics; Belief revision; Deontic logic.

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