Logic in theory and in practice : the normative status of logic

Abstract

In my thesis, I address the question ʽWhat normative status does logic have?', to argue that logical normativity is of a weak sort, and that its constraining power is similar to that of recommendations. The thesis first discusses the notion of logical validity and logical formality, then asks whether logic is a priori and whether it can provide a priori norms for thinking. Subsequently, the issue of the bridge principles linking formal logic to informal reasoning is addressed, jointly with a brief discussion of the deontic operators included in the bridge principles. Then, the thesis addresses three criticisms of the normative role of logic with respect to rational reasoning. The first criticism is discussed in the fourth chapter; it starts from the consideration of the cognitive limitations of human agents and discusses a model of rationality that takes those limitations into account. The second criticism is analyzed in the fifth chapter; it is motivated by the empirical studies in the psychology of reasoning, and discusses human reasoning from a descriptive point of view, lending support to the model of rationality presented in the fourth chapter. The third criticism, presented in the sixth and final chapter, addresses the normative role of logic from an a priori point of view, showing how the epistemic paradoxes are crucial for determining what normative import logic has on rational reasoning. The final chapter defends the main thesis that logic has a weak import on our reasoning, which resembles a recommendation rather than an obligation.