I have long been struck by the fact that we do not simply survive but navigate this world quite successfully despite all the irrational beliefs we are inclined to adopt and hang on to. This book is an attempt to make sense of the idea that our undesirable and at times cringeworthy irrationality may support our way to succeed as imperfect agents. (Bortolotti 2020, p. 1) So begins Dr Lisa Bortolotti’s excellent new book, The Epistemic Innocence of Irrational Beliefs (henceforth TEIIB). Of course, the observation that irrational beliefs can bring practical benefits is not an original one. Philosophers and psychologists, including Bortolotti herself (2014), have long drawn attention to the role that irrational beliefs can play in promoting various kinds of practical success, delivering psychological (Taylor and Brown 1988), social (Williams 2020), and biological benefits for their believers (McKay and Dennett 2009). TEIIB breaks genuinely new ground in this area, however. According to Bortolotti, epistemically irrational beliefs can—in fact, frequently do—promote not just practical success but epistemic success. Specifically, such beliefs often promote our epistemic functionality, our ability to pursue and attain epistemic goals, producing significant epistemic benefits that could not—or at least could not as easily—be attained by more rational beliefs. To capture such cases, Bortolotti argues that we need a new concept: epistemic innocence.