Argumentation 17 (3):335-346 (2003)

Classic deductive logic entails that once a conclusion is sustained by a valid argument, the argument can never be invalidated, no matter how many new premises are added. This derived property of deductive reasoning is known as monotonicity. Monotonicity is thought to conflict with the defeasibility of reasoning in natural language, where the discovery of new information often leads us to reject conclusions that we once accepted. This perceived failure of monotonic reasoning to observe the defeasibility of natural-language arguments has led some philosophers to abandon deduction itself (!), often in favor of new, non-monotonic systems of inference known as `default logics'. But these radical logics (e.g., Ray Reiter's default logic) introduce their desired defeasibility at the expense of other, equally important intuitions about natural-language reasoning. And, as a matter of fact, if we recognize that monotonicity is a property of the form of a deductive argument and not its content (i.e., the claims in the premise(s) and conclusion), we can see how the common-sense notion of defeasibility can actually be captured by a purely deductive system
Keywords default logic  exceptions  monotonicity  practical generalizations  validity
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DOI 10.1023/A:1025164703468
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References found in this work BETA

Problems in Argument Analysis and Evaluation.Trudy Gover - 2018 - Windsor: University of Windsor.
A Critique of Pure Reason.Drew McDermott - 1987 - Computational Intelligence 3:151-60.
Logic: Techniques of Formal Reasoning.Donald Kalish, Richard Montague & Gary Mar - 1964 - New York, NY, USA: Oxford University Press USA.
A Logic for Default Reasoning.Ray Reiter - 1980 - Artificial Intelligence 13 (1-2):81-137.

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Citations of this work BETA

Monotonicity and Reasoning with Exceptions.Frank Zenker - 2006 - Argumentation 20 (2):227-236.
Reasoning From Conflicting Sources.Gilbert Plumer & Kenneth Olson - 2007 - In Hans V. Hansen, Christopher W. Tindale, J. Anthony Blair, Ralph H. Johnson & David M. Godden (eds.), Dissensus and the Search for Common Ground. Proceedings 2007 [CD-ROM]. Ontario Society for the Study of Argumentation. pp. 1-9.

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