How to conquer stupidity by Leo Markun is a concise self-help and popular-philosophy essay written in the early 20th century. The book argues that “stupidity” is best understood as poor or disordered thinking and response, and it outlines how clearer reasoning, better habits, and critical inquiry can overcome it. The author first widens the definition of stupidity, shows its relativity to context, and questions the value of intelligence tests and other crude measures, noting that mental capacity is limited but mental attainment can grow through education rightly understood as method and order. He then teaches how to think: build experience, keep ideas accessible, and, above all, impose order; treat thinking as problem-solving; distrust blind faith, slogans, and authority; practice self-control, humility, humor, and an objective view of oneself. He explains the stages of thought (preparation, incubation, illumination, verification), urges patience with incubation and rigor in checking insights, and advises relying on experts while accepting suspended judgment when evidence is thin. Applying this to public life, he dissects partisan politics, war talk, economic nostrums, and the social sciences, urging a scientific temper and warning against Bacon’s “idols” and common biases tied to religion, race, class, mobs, age, and illness. He concludes that the surest way to conquer stupidity is to cultivate steady, self-critical, evidence-based, and orderly reasoning in everyday affairs.