One of the most important things that the Darwinian revolution affects is the previous teleological thinking. In particular, the attribution of functions to various entities of the natural world with explanatory pretensions. In this change, his theory of natural selection played an important role. We all agree on that, but the diversity and heterogeneity of the answers that try to explain what Darwin did exactly with functional biology are overwhelming.In this paper I will try to show how Darwin modified previous functional biology. For pre-Darwinian naturalists did not hesitate to attribute functions in which, for example, the traits of one species were in the service of other species.I will try to show that this has consequences on the discussion regarding the nature of functional language. I will try to show that the main approaches, the systemic and the etiological, do not adequately account for these changes and therefore do not account for the way functional biology regulates the kind of legitimate functions.I will outline a possible new solution to this problem: appropriate functional attributions in Darwinian functional biology could be regulated by a theory or a set of laws that provide the criteria for determining its fundamental concepts.