The modern approach in economics teaching registers the mainstream attack over the elementary logics of human action. In the present approach, I am going to stop the attempts over the economic science foundations, by destroying the two myths, more or less new, only seeming harmless, such as “zero opportunity cost” and “negative marginal utility” myths. Those errors – perpetuated in school books, courses halls and scientific university lectures – undermines the economics right knowing and getting a healthy way of economic thinking within the pupils, students and other individuals interested in economics logic. Being in the economic way of thinking service and (authoritative) being responsible for the destiny of the ideas he promotes, the economist, author of school books, must start in a simple way, with the necessity of discerning between correct and incorrect ideas.