Vladimir Putin’s invasion of Ukraine came as a shock to most of the world. It is so blatantly unreasonable and reprehensible that some commentators have questioned Putin’s mental health and capacity for rational action. The debates about Putin’s rationality are, however, muddled by a lack of clarity about what we mean by ‘rationality’. Two types of irrationality There are two senses in which Putin clearly is irrational. First, the beliefs that motivated his invasion were not produced by a rational consideration of evidence and arguments, nor can they be rationally justified. He appears to have developed an increasingly warped and extreme view of things, including myths, propaganda, and “alternative facts”…