SOPhiA 2022

Salzburgiense Concilium Omnibus Philosophis Analyticis

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Programm - Vortrag

Imprädikationen und die Paradoxa der Normenlogik
(Logic/Philosophy of Mathematics, Englisch)

Deontic Logic aims at describing, through the instruments of Symbolic Logic, the rules underlying sound reasoning in normative contexts. Modern Deontic Logic was built analogously to the various logics of descriptive language, i.e., to Propositional, Predicate and, above all, to Modal Logic. This structure, however, is prone to recognizing certain deduction forms, which, from an intuitive point of view, are evidently incorrect, as being nonetheless logically valid. These are the so-called paradoxes of Deontic Logic. E.g., Ross' paradox: from an atomic sentence such as "deliver the letter!", one derives a disjunctive normative sentence like "deliver the letter or burn it!".

The goal of constructing a system of Deontic Logic free of paradoxes has led to the development of many logical systems. This venture's degree of success is questionable. While many paradoxes can be easily avoided, the development of new, ever more complex systems has also led to the discovery of new paradoxes. At the same time, normative Sciences, such as Practical Philosophy and Law, have been dealing with normative reasoning for centuries. Particularly, Legal Methodology has developed a canon of widely accepted argument forms. Moreover, as it is well known, the paradoxes of Deontic Logic pose no particular problem to jurists or moral philosophers. Thus, it seems reasonable to attempt to construct Deontic Logic as a formalization of Legal Methodology.

However, Legal Methodology is based on arguments - e.g., analogy, arguments a fortiori or e contrario -, which are, from a logical point of view, fallacies. Turning them into logically sound arguments requires the addition of further premises. In this contribution, I argue that this premise-addition also leads to paradoxes. This is due to the fact that Legal Methodology is based on impredicative concepts (e.g., similarity, context) which are not fully representable in classic symbolic logic.


Chair: Maren Bräutigam
Zeit: 14:40-15:10, 07. September 2022 (Mittwoch)
Ort: SR 1.004

Diogo Campos Sasdelli
(Universität Vechta, Deutschland)



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