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In The Enigma of Reason: A New Theory of Human Understanding (Harvard, 2017; Paperback 2018), Hugo Mercier and Dan Sperber claim to offer a novel account of human reasoning. “What reason does,” the book summary explains, “is help us justify our beliefs and actions to others, convince them through argumentation, and evaluate the justifications and arguments that others address to us.”
The book lays out an “interactionist” approach to human reasoning and contrasts it to the “intellectualist” approach. The latter is the standard formulation, which assumes reasoning is valuable because it helps humans arrive at more accurate conclusions about the world. In contrast, their interactionist approach emphasizes the evolutionary argument that our ancestral socio-linguistic environment shaped the architecture of human reasoning and reason-giving.
Specifically, the authors posit that there are two closely related components to human reasoning, which they call the “argumentative” and “justifying” functions. The argumentative function allows individuals to persuade skeptical others about one's beliefs, as well as the capacity to determine the legitimacy of others’ claims. The justifying function enables humans to generate accounts to themselves so that they can better present their behavior in a socially justifiable manner. In the words of the authors (p. 8), “By giving reasons in order to explain and justify themselves people indicate what motivated and, in their eyes, justifies their ideas and actions.”
I found much to like in the authors' arguments. As regular readers of this blog know, the Justification Hypothesis (JH) offers almost an identical account of human reasoning. The JH is the idea that humans are "the justifying animal," and that human cognition and consciousness are different from other animals because the problems associated with justifying one's actions and analyzing the justifications and arguments of others in a sociolinguistic environment.
Fifteen years ago, in Henriques (2003, p. 172), I summarized the Justification Hypothesis as follows: “Effectively justifying one’s actions was a new, difficult and extremely important adaptive problem to solve, precisely the type to lead to strong selection pressures and rapid evolutionary change. Solving the problem of justification requires new cognitive capacities, such as self-representation, generating causal explanations for why one behaved a certain way and evaluating the legitimacy of others’ actions.” This is exactly the “interactionist” framework for the structure of human reasoning that Mercier and Sperber posit.
Evidence for the overlap increases when we examine the implications of this idea. For example, a major thesis of The Enigma of Reason is that the formulation explains key features of human reasoning, such as self-serving (or "myside") biases. In addition, the authors argue that their model accounts for the fact that humans reason better in social contexts with social frames than in purely analytic ones.
These insights also line up with the JH. In a section explicitly about how the JH accounts for self-serving biases in that 2003 paper, I explained that, “According to the JH, people should tend to explain their behavior and the things that happened to them in a manner that affords the most social influence” (p. 173). And in a separate section explaining how the JH accounts for biases in human reasoning capacities more generally, the description offered was as follows: “The JH further suggests that the general reasoning capacity in humans emerged out of determining what is and what is not justifiable in the social context. This gives rise to another implication of the JH. If social reasoning gave rise to general reasoning, then humans should be particularly adept at social reasoning, at least in comparison with other forms of general reasoning. This is precisely the case.” (p. 175). In short, the central ideas about human reasoning put forth in The Enigma of Reason correspond directly to ideas put forth in the Justification Hypothesis.
I will summarize this brief blog by saying I think the authors' are onto a very important insight about human reason. Their ideas are almost identical to an insight I had over 20 years ago, and that has been the subject of many subsequent publications.
One enigma does remain, however. One wonders why, if the JH is so similar to the thesis of this book, didn't Mercier and Sperber review or cite it, but rather claim that theirs is a new idea? That is the "real" enigma. For readers who are interested in learning more about this interesting side of the story, see here for full description of the situation and here for a more complete blog on what has happened.
