As many have pointed out, the cognitive type of the unicorn, later on spread like wildfire in western culture, has one of its prototypes in Ctesias’ Indian ass, described for the very first time in his Indika (FGrHist 688 F 45, 45 and 45q = Ael. NA IV 52). Over the last two centuries, several scholars have raised questions on the real extra-linguisitc referent: what had the Physician of Cnidus really talked about in his account? An Indian rhino? A bull? An antelope? Or was it a fake, good to implement his ethnographic fiction on the extreme peripheries of Persian empire? Whatever Ctesias’ Indian ass was, Aristotle (HA 499 b 15-31) shows no hesitation in believing in its effective existence, and accepts it as a part of the animal kingdom. This happens because some of the zoological features of the paradoxical beast are not so incompatible with the etiological system developed in De partibus animalium.

Can Cicero’s De officiis be considered as an excuse for justifying and supporting the common idea that rights, aid and solidarity have been reserved only to those are “close” to us? In the current debate concerning the real universality and the value of human rights, the interpretation of the last work of Arpino’s author, framed in its historical and cultural context, may contribute to a fair restitution of the meaning we assume for the virtue named ratio societatis et communitatis.