The outline of the paper is as follows: in Section 1, I first introduce what I hold to be the two basic assumptions characterizing the standard approach to reasoning and then show how these two assumptions constrain the picture of reasoning emerging from today’s most prominent psychological theories of reasoning. In Section 2, I criticize this picture because it represents reasoning as a self-centered cognitive activity, unfolding outside the reasoner’s awareness, whose function is fundamentally instrumental. In Section 3, I turn to Hugo Mercier and Dan Sperber’s argumentative theory, according to which reasoning has an interpersonal function, being evolved so as to evaluate others’ arguments and to justify our own conclusions and decisions. In Section 4, starting from some ideas about human rationality presented (in a non-systematic way) by Paul Grice which Marina Sbisà has recently presented under the label argumentative rationality, I first distance myself from Mercier and Sperber’s theory, as they too emphasize the rhetorical (and so instrumental) function of reasoning, and then outline an alternative picture of it which focuses not only on our ability to justify our conclusions and decisions, but also on our motivations (that is, our concern) to do so. I then conclude by making some suggestions as to the importance of studying reasoning in natural interactional situations where people ordinarily take care to justify what they say and do.
