How can members of a species that discovered symbolic logic and the double helix also believe that the earth is flat and that Hillary Clinton ran a child-sex ring out of a pizzeria? Human rationality is very much in the news, as we struggle to understand how an era with unpreceded scientific sophistication could harbor so much fake news, conspiracy theorizing, and “post-truth” rhetoric. Rationality has also long been a foundational topic in the academy, including philosophy, psychology, economics, mathematics, and government. Part I of “Rationality” covers the nature of...