It all starts with a question: how and why did human beings acquire the ability to reason? The standard answer is that reason exists to assist with decision making. We assume that reason emerged under selective pressure favouring smartness. It’s survival of the most accurate! The ‘fittest’ are those most adapted to figuring out what is real and true about the world. As a Darwinian explanation, this seems reasonable enough.
Or is it?
With his colleague Dan Sperber, Mercier proposes a counter hypothesis: what if the original function of reason was not to make ‘right’ or ‘correct’ predictions or observations about the world, but to convince other people to think or act differently?
If you want someone else to do something, walking up to them and barking an order is highly ineffective. Even if commanding from a hierarchical position of authority, you still accept that influencing the actions of another human is a nuanced affair. To change what someone does, you have to change something about the way they think. You have to give them an insight into why your idea is a good idea. They need to buy it. Trust is crucial. In short, even the simplest act of influencing another person requires you to reason with them.
In this account, reason emerges primarily to serve a social function. The original, adaptive purpose of reason was not to reach correct and factual conclusions about the world but to convince one another about our ideas — beliefs about how we should organize, behave, and work together. For Mercier, this theory goes a long way to explaining why our reasoning is so prone to bias and groupthink. Reason evolved socially, not by solitary philosophers roaming around and coming up with scientifically factual observations about the world. (The practice of intentional, self-aware objectivity is only a particular ‘use case’ for reason that develops far down the evolutionary line.)
This social model for the evolutionary origin of reason goes a long to explaining why we tend to strongly favour what we already believe and why we excel at using reason to justify our prejudice and bias. After all, if the original purpose of ‘reason 1.0’ was to enable us to function and communicate as a group, we should not be unsurprised that our capacity to self-organize around ideas far outperforms our devotion to sober, detached analysis. In evolutionary terms, group inclusion equals survival, making group identity primal and paramount.
Consider the modern implications. For instance, we might look at the concept of ‘conclusive evidence‘ itself as a socially constructed and group-dependent cognitive framework: using evidence to make decisions is only an effective strategy to the extent that you are part of a group that shares your convictions about evidence in the first place.
The ramifications of Mercier and Sperber’s theory are significant. It invites us to critically rethink what it even means ‘to reason with someone’ in the first place. To suppose that presenting another person ‘with the facts’ is a coherent strategy for changing their minds is, perhaps, a mythology its own.