That's a question more and more difficult. Why ? Because we lost the background offered by theology, but also, and more deeply, because we have forgotten - as our language retains traces - the basic structure of a virtue ethics of Aristotelian obedience. Here is the basis of the ethical-metaphysical structure which, basically, is nearing a theological pattern: "a fundamental opposition between man as he is and man as he could be if he realized his nature essential "; Ethics is a science (knowledge) for "men to understand how they spend the first state to the second." Thus, man has, in Aristotelian ethics, three elements to orient themselves morally, "a conception of human nature as it is, the design of the precepts of rational ethics and the nature of design human as it could be if it achieved its telos. " This articulation of traditional invoice is lost when we bow to the idea that "no valid reasoning can go from completely factual premises (be) a moral or evaluative conclusion (have to be)." However, there are functional concepts that take their factual premises assessment functions. For example: "the factual premises as" his yield per hectare is better than all the farmers of the region "(...) and" cattle won all the first prizes in agricultural competitions, "we can draw a valid evaluative conclusions "this is a good farmer. '" And, of course, classical and medieval conceptions "use at least one central functional concept, the concept of"