A Response to Hugo Mercier and Dan Sperber's “Why Do Humans Reason? Arguments for an Argumentative Theory”

In their recently published discussion of why humans reason, Hugo Mercier and Dan Sperber (2011a) pose a question that on its face appears to be metaphysical in nature and, hence, suitable primarily for unverifiable speculation. However, as the piece unfolds, one is left less with this perception of the issues and more with an appreciation of the authors' effort to expand the domain of reasoning beyond narrowly and commonly conceived epistemic functions to the social realm in which collective decision making is occurring and participants seek to exercise influence. To that end, they advance the view that "the function of reasoning is argumentative" and that from this perspective it serves "to devise and evaluate arguments intended to persuade" (p. 57). In developing the thesis, which initially comes across as excessive, the authors eventually concede that persuasion is neither the only function of reasoning nor the exclusive motivation humans have when engaging in it. Rather, persuasion, they claim, is the main function of and motivation for reasoning. Even this more inclusive characterization, however, still strikes one as excessive, as well as likely unnecessary to derive benefit from the insights to which reading the article exposes one in efforts to understand reasoning as a form of human activity. The restrictions that Mercier and Sperber (2011a) impose on the functions of reasoning and the motivations behind it may be a reflection of the seeming teleological origins of their perspective and clearly are a reflection of its grounding in evolutionary psychology. Irrespective of the influences, to claim that persuasion is the main function of and motivation for reasoning, even if limited to social situations in which two or more individuals are attempting to arrive at a collective decision, seems to impose a burden of proof that would be difficult to satisfy. Why it is insufficient simply to acknowledge that these aspects of reasoning make sense on intuitive grounds, have a certain resonance with many people's lived experience, have received limited scholarly attention, and may lead to different understandings of what constitutes skill in reasoning, or the lack thereof, among humans escapes me. Even the authors appear to be tentative in advancing the claim: In principle, several effects of a trait may contribute to fitness, and hence a trait may have more than a single function. Even then, it may be possible to rank the importance of different functions, and in particular to identify a function for which the trait is best adapted as its main function. (p. 59) Even if scholars could realistically satisfy the rather formidable burden of proof for justifying claims concerning the main function of reasoning and principal motivation for engaging in it, Mercier and Sperber (2011a) provide little guidance concerning how to determine, let alone confirm, that reasoning is best adapted for enabling "people to exchange arguments that, on the whole, make communication more reliable and hence more advantageous" (p. 60). In fairness, it presumably was not their intention to advise readers about the design of pertinent investigations. On the other hand, some indication of how best to test the hypothesis embedded in the opening paragraph would be of value. At minimum, it would seem necessary for one to have: (a) access to large numbers of dyads and groups performing decision-making tasks in not only controlled research environments, but in naturalistic settings as well; (b) reliable methods for recording the ongoing interaction of the participants for the duration of the task; and (c) suitable measures of both the various functions of reasoning, defined as "the mental act of constructing or evaluating an argument that is at least partly explicit" and "must contain both a conclusion and reasons to accept this conclusion" (Mercier & Sperber, 2011b, p. …