This course, entitled "Rationality", delves into one of the most extraordinary abilities of human beings: the ability to reason and make sense of nature in exquisite detail. However, despite this ability, individuals often fall prey to irrational judgments and decision making. The aim of this course is to provide a comprehensive guide to thinking more clearly and avoiding common cognitive biases. It will equip participants with the tools to navigate and survive in a society where irrationality is prevalent, providing strategies for identifying and avoiding these biases in everyday life and in decision-making. Ultimately, this will enable individuals to make more informed and rational choices that lead to a better quality of life.