This lecture explores the mindset of individuals who believe in irrational things, leading them to adopt behaviors or beliefs contrary to common sense. It delves into examples such as taking on more debt to pay off existing debts, attempting to quit drinking by sheer willpower, and believing in a literal interpretation of the creation story. The lecture discusses the concept of irrationality as a mode of thinking that defies logic and sometimes opposes reason. It also examines how irrational beliefs often stem from a rejection of science and scientific progress, using the case of creationists in the USA as a focal point.