Georg Brun

Traditional logical reconstruction of arguments aims at assessing the validity of ordinary language arguments. It involves several tasks: extracting argumentations from texts, breaking up complex argumentations into individual arguments, framing arguments in standard form, as well as formalizing arguments and showing their validity with the help of a logical formalism. These tasks are guided by a multitude of partly antagonistic goals, they interact in various feedback loops, and they are intertwined with the development of theories of valid inference and adequate formalization. This paper explores how the method of reflective equilibrium can be used for modelling the complexity of such reconstructions and for justifying the various steps involved. The proposed approach is illustrated and tested in a detailed reconstruction of the beginning of Anselm’s De casu diaboli.

Decision theory explicates norms of rationality for deriving preferences from preferences and beliefs. Empirical studies have found that actual preferences regularly violate these norms, launching a debate on whether this shows that subjects are prone to certain forms of irrationality or that decision theory needs to be revised. It has been claimed that such a revision is necessitated by the fact that normative uses of decision theory must be justified by a reflective equilibrium. The paper discusses three points. First, the debate over the impact of empirical studies on decision theories is only meaningful with respect to a decision theory that includes not only a formal system but also a theory of application. Second, differences in the concepts of reflective equilibrium appealed to are a source of confusion in the debate on rationality. Third, the assumption that normative uses of decision theory are justified by reflective equilibrium is not sufficient ground for arguing that the empirical studies call for a revision of decision theory. Such an argument must rely on substantive claims about rationality, preferences and beliefs.