The truth is. The Enigma of Reason. According to their theory of reasoning, reason’s primary strengths are justifying beliefs we already believe in and making arguments to convince others. While this kind of reasoning helps us cooperate in a social environment, it does not make us particularly good at truth-seeking. It also makes us fall prey to a number of cognitive biases, like confirmation bias, or the tendency to search for information that confirms what we already believe.
Their ideas also help explain why politics seems to make us so bad at reasoning. If most of reasoning is for social cohesion instead of truth-seeking, then belonging to a particular political party should distort our reasoning and make us pretty bad at finding the truth.