[Revised entry by Robert Koons on June 13, 2025.
Changes to: Main text, Bibliography, suppl7.html]
Reasoning is defeasible when the corresponding argument is rationally compelling but not deductively valid. The truth of the premises of a good defeasible argument provide support for the conclusion, even though it is possible for the premises to be true and the conclusion false. In other words, the relationship of support between premises and conclusion is a tentative one, potentially defeated by additional information. Philosophers have studied the nature of defeasible reasoning since Aristotle’s analysis of…

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