Why Proposers and Disposers need to be kept distinct: The Argumentative Theory of Reasoning

The ‘argumentative theory of reasoning’ (conceptualized by Dan Sperber and developed with the evolutionary psychologist Hugo Mercier) hypothesizes that reasoning serves two distinct survival-related functions: a) convincing people and b) evaluating the arguments of others – ‘thereby allowing communication to proceed even when trust is limited’ (Landemore, 2013, p. 126). The theory – developed as an evolutionarily-plausible alternative to the classical (Cartesian) model of reasoning as a way of updating and correcting one’s own beliefs – is based on the distinction between performing speech acts and evaluating the performative utterances of others:

According to this theory, individual reasoning works best when used to [a] produce and [b] evaluate arguments during a public deliberation. It predicts that when diverse opinions are discussed, group reasoning will outperform individual reasoning. (Mercier & Landemore, 2012, p. 243)

‘Exposing people to disagreement and debates increases their ability to entertain different opinions . . . either by witnessing a debate or by being part of one’ (ibid., p. 252). The important factor is not participation in speech acts so much as ‘the presence or expression of dissenting opinions in deliberative settings’ (ibid., p. 254, my emphasis). (Mercier & Sperber, 2017) also point out that as a species we are much better at evaluating reasons than producing them – I may not be able to see the beam in my own eye, but I can find the mote in yours. Laboratory studies indicate that we are better able to find the flaws in our own reasons when we believe those reasons to have been produced by someone else, thereby supporting the case for the division of labour between persuaders and evaluators, as it’s very hard to change one’s mind about one’s ‘own’ (i.e. indigenous) convictions.

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