Teleology is still a source of embarrassment for the natural sciences and in particular for biology that seems unable to describe and explain the genesis and structure of life without it. How is it possible for something not yet existing to determine the occurrence of what is temporally prior to it? How can the future cause the present and the past? In what follows we intend to examine the elaboration of the biological notion of «teleonomy» through the writings of Ernst Mayr, in order to verify its rigor and strenght with respect to the criteria of scientificity adopted by Mayr himself, in particular with respect to the adoption of the cybernetic model. On the one hand, to show the consistency of the debt that the so-called scientific discourse owes to the philosophical tradition, where it elaborates notions that claim to be emancipated. On the other hand, to detect, within the scientific discourse itself, the limits that a certain position that claims to be scientifically founded can impose on research, becoming a dogmatic assumption.