Abstract

Logic, considered as a technical discipline inaugurated by Aristotle and typically represented by the variety of the modern logical calculi, constitutes a clarification and refinement of a conviction and practice present in common sense, that is, the fact that humans believe that truth can be acquired not only by immediate evidence, but also by means of arguments. As a first step logic can be seen as a “descriptive” record of the main forms of the arguments present in common sense, but the fact that some of these patterns can actually allow for the derivation of false consequences from true premises imposes the task of making explicit what patterns correspond to a “correct reasoning” and what not. At this point logic appears endowed with a “normative” characteristic. This amounts to saying that logical calculi are intended to adequately mirror the intuitive notion of “logical consequence” and in this sense they cannot be totally arbitrary or conventional, but must satisfy certain basic requirements such as the conditions of soundness and of semantic completeness. In such a way they are “judged” according to the fundamental requirements present at the level of common sense and appear as “idealizations” of the kinds of reasoning practiced in common sense. For this reason also several kinds of logical calculi are fully justified since they make explicit in an idealized form the concrete ways of reasoning that are imposed by the particular domain of reference of the discipline in which they are used and which are basically recognized in common sense.