This essay is born from the need to clarify some of the errors that the orthodox economics textbooks promote, sometimes with fair nonchalance. Such an error can be identified from the very first "economics lesson" - the lesson of the "economics way of thought" that seeks to explain human action by using the counterfactual term "opportunity cost". All the errors promoted in economics textbooks, courses or "scientific" conferences undermine the correct knowledge of economics and the inheritance of a healthy economic thought from those interested in the logics that lies beneath economics.