Abstract

One of the key concepts in the Philosophy of Logic is the notion of inference. In this paper we expand the notion of logical inference and describe its role in a comprehensive theory of rationality. Some recent rationality theories either presuppose an unattainable logical capacity or they minimize the role of logic, in light of the vast amount of data on fallacious inferential performance. In this paper we defend the view that logical acuity, redefined to include heuristics, is a necessary factor in rationality. We evaluate some presuppositions of algorithmic models and some normative and metatheoretical properties of heuristic models, and defend our model against possible objections. Our revised notion of logical inference functions as the nucleus of the notion of logical acuity which in turn is a necessary building block for a realistic model of rationality. This model emphasizes the logical role of inferential heuristics, cognitive constraints and contextuality, introduces concepts such as "obvious inference", "cautious deductive closure", and "familiarity", and develops the notions of cognitive economy and contextual limitations as tools for evaluating and predicting rational behavior.