How Mercier and Sperber reframe reasoning as justification and argumentation in human interaction.
Overview
Mercier and Sperber’s The Enigma of Reason challenges one of the most entrenched assumptions in cognitive science: that reason evolved primarily to improve individual knowledge and decision-making. Instead, they argue that reason is best understood as a social adaptation, designed to justify our actions and persuade others. This reframing positions reason not as a solitary truth-seeking faculty, but as a tool for navigating the complexities of human cooperation and communication.
Previous works such as Kahneman’s Thinking, Fast and Slow (2011), building on his collaboration with Amos Tversky, summarized decades of research revealing flaws in reasoning. Much of human decision-making relies on mental shortcuts or heuristics, characteristic of System 1 thinking, which depend in part on intuitions shaped by regularities in nature. Kahneman emphasized the slow and effortful work of System 2 thinking as necessary for better judgments, yet flawed judgments persist. Mercier and Sperber avoid weighing in directly on the System 1/System 2 debate. Instead, they focus on how our brains infer relationships between events in the environment to pursue courses of action without relying on formal reasoning. In short, we are largely unaware of the reasons or inferences quickly occurring within our minds.
Although the authors devote limited attention to moral reasoning, their claims resonate with Jonathan Haidt’s work on moral foundations, which emphasizes the role of intuitions in producing the judgments we later justify or critique—a topic I and my colleagues have explored elsewhere (Sutton & Schmidly, 2016; Sutton et al., 2019).
Cite this review
Sutton, G. W. (2025, December 14). The Enigma of Reason: Rethinking cognition as social adaptation: How Mercier and Sperber reframe reasoning as justification and argumentation in human interaction. Interdisciplinary Book Reviews. https://suttonreviews.suttong.com/2025/12/the-enigma-of-reason-rethinking.html
Contribution to Cognition
Mercier and Sperber’s central claim reshapes how we think about cognition in two important ways:
1. Reason functions to justify our behavior to our social group.
Reason enables individuals to explain and defend their actions, providing the scaffolding for coordination in social groups.
By offering justifications, people establish credibility, negotiate responsibilities, and stabilize norms. Reason creates and preserves a reputation.
Cognition here is not about internal accuracy, but about external coherence—making one’s behavior intelligible to others.
2. Reason functions to communicate with others when engaged in two-way argumentation.
Reason equips us with arguments to persuade others to accept our perspective. When simple reasons suffice, we avoid the extra cognitive effort required for more sophisticated analyses. The authors view this aspect as a natural tendency to being lazy.
Reason functions more effectively at criticizing the arguments of others than at discovering flaws in our own arguments, due to pervasive myside bias. This bias protects us from quickly accepting another person’s point of view.
Importantly, reasoned debate in groups can result in better judgments than solitary reasoning.
Dimensions of Reason
Post-facto role: Reason often justifies conclusions after they are reached, rather than guiding them.
Reputation management: Anticipating social scrutiny, individuals proactively generate reasons to protect credibility.
Social context: Reasons are simplified, normative accounts of mental states, shaped to fit social expectations.
Task-specific reasoning: Logic plays only a marginal role; reasoning occurs in various modules, which are tuned to specific problems and opportunities.
Beyond awareness: Reasons as inferences occur quickly. We often respond to sensory input based on the regularity in our environment.
Meta-level reasoning: What we call reasoning, is more like reasoning about the lower level reasons than our responses to various external or internal events.
Evaluation
Mercier and Sperber’s contribution to cognition lies in reframing reason as a socially adaptive meta-function rather than primarily a truth-seeking tool. The fact that reason is flawed is not surprising, and they cite research which supports this claim. What is novel is the argument that effective social interaction is the primary function of reasoning—a claim that deserves further exploration.
The book also introduces readers to extensive research on the problems of relying on reasons people give for their behavior as true accounts of why they acted as they did. Humans lack access to all the information about environmental factors and brain activity that shape behavior. As such, the search for motives is inherently flawed, despite the persistent popularity of crime dramas and the endless quest for reasons behind romantic or interpersonal behavior.
As a clinician, I suggest that reason is not merely about offering socially acceptable justifications to fit in. It can serve a crucial survival function when faced with accusations that, if not successfully rebutted, could lead to imprisonment or even death.
I recommend this book to anyone interested in a summary of psychological research and thinking at the time it was written. In addition, I think psychotherapists and those who conduct interviews should be keenly aware of the social function of reasons to justify behavior and concomitantly the inherent difficulty in providing a valid explanation for the causes of their behavior—especially when we consider the problems of human memory.
Closing Thought
The Enigma of Reason is a provocative and illuminating work that redefines the role of reason in human cognition. By situating reason within the dynamics of social life, Mercier and Sperber provide a framework that not only explains our biases and post-hoc justifications but also highlights the adaptive value of reasoning in fostering cooperation and communication.
References
Kahneman, D. (2011). Thinking, fast and slow. Farrar, Straus and Giroux.
Mercier, H., & Sperber, D. (2017). The enigma of reason. Harvard University Press.
Sutton, G.W. & Schmidly, B. (eds.) (2016). Christian morality: An interdisciplinary framework for thinking about contemporary moral issues. Pickwick.
Sutton, G. W., Kelly, H. L., & Huver, M. (2019). Political identities, religious identity, and the pattern of moral foundations among conservative Christians. Journal of Psychology and Theology, 48, pp. 169-187.
Post Author
Geoffrey W. Sutton, Professor Emeritus of Psychology at Evangel University, holds a master’s degree in counseling and a PhD in psychology from the University of Missouri-Columbia. His postdoctoral work encompassed education and supervision in forensic and neuropsychology and psychopharmacology. As a licensed psychologist, he conducted clinical and neuropsychological evaluations and provided psychotherapy for patients in various settings, including schools, hospitals, and private offices. During his tenure as a professor, Dr. Sutton taught courses on psychotherapy, assessment, and research. He has authored over one hundred publications, including books, book chapters, and articles in peer-reviewed psychology journals.
Find chapters and essays on Substack. [ @GeoffreyWSutton ]
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