Logica Universalis

, Volume 4, Issue 2, pp 225-239

First online:

The Place of Logic in Reasoning

  • Daniel KayserAffiliated withLIPN, UMR 7030 du CNRS, Institut Galilée, Université Paris-Nord Email author 

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Reasoning is a goal-oriented activity. The logical steps are at best the median part of a full reasoning: before them, a language has to be defined, and a model of the goal in this language has to be developed; after them, their result has to be checked in the real world with respect to the goal. Both the prior and the subsequent steps can be conducted rationally; none of them has a logical counterpart. Furthermore, Logic aims at prescribing what a correct reasoning is. But correct with respect to what? If the answer is: with respect to truth, the next question is whether the truth in everyday life, physics, economy, is the same as the truth that logicians have in mind. Resorting to Logic is justified only if an idealization in terms of true propositions in the logical sense is compatible with the goal. If such an idealization is legitimate, so is the use of classical Logic. If not, there is no authority forbidding to skew Logic in order to better reflect the nature of the reasoning required for the task.

Mathematics Subject Classification (2010)

Primary 68T27 Secondary 03B65


Everyday life reasoning rationality natural language nonmonotonic logic