This small book analyzes and comments on the following question: are there idiots or fools in the world? What is their role in society? The author argues that they do not exist and that for the evolution of societies, intelligence does not matter, as some claim, but individual and collective interests do. When people are free to act within a framework of legal and ethical rules, society develops. When people are not free or are free without laws and rules, society declines. Instead of the laws of stupidity, for understanding social evolution, this book proposes the laws of interest. For this reason, it examines in parallel two texts that deal with this issue, Carlo P. Cipolla's book "The Basic Laws of Human Stupidity" and the older text by Evangelos Lembesis "The Tremendous Importance of Fools in Contemporary Life," which is included in its entirety at the end of the book.