The notion of ideal is surely one of the most important legacies of Western philosophy, yet it has been much neglected by contemporary philosophy, probably because of the negative destiny it has suffered during the last century, by being firstly abused through forms of totalitarianism and secondly censured through forms of anarchism. But there are two interesting exceptions: two monographs written by two noteworthy philosophers, the first being Nicholas Rescher, who published in 1987 Ethical Idealism. An Inquiry into the Nature (...) and Function of Ideals, and the second being Dorothy Emmet, who published in 1994 The Role of the Unrealisable. A Study in Regulative Ideals. In this article I shall take into account their positions arguing that both Rescher and Emmet work on a very important topic, as they highlight the essential role the notion of ideal played, and still plays, in human life, yet, the role of the notion of ideal they highlight may be notably increased by more precisely understanding its own genesis and history. (shrink)