M. TVLLI CICERONIS DE OFFICIIS LIBER PRIMVS
 Sed quoniam, ut praeclare scriptum est a Platone, non nobis solum nati sumus ortusque nostri partem patria vindicat, partem amici, atque, ut placet Stoicis, quae in terris gignantur, ad usum hominum omnia creari, homines autem hominum causa esse generatos, ut ipsi inter se aliis alii prodesse possent, in hoc naturam debemus ducem sequi, communes utilitates in medium adferre, mutatione officiorum, dando accipiendo, tum artibus, tum opera, tum facultatibus devincire hominum inter homines societatem.
 But since, as Plato has admirably expressed it, we are not born for ourselves alone, but our country claims a share of our being, and our friends a share; and since, as the Stoics hold, everything that the earth produces is created for man's use; and as men, too, are born for the sake of men, that they may be able mutually to help one another; in this direction we ought to follow Nature as our guide, to contribute to the general good by an interchange of acts of kindness, by giving and receiving, and thus by our skill, our industry, and our talents to cement human society more closely together, man to man.
Source: Marcus Tullius Cicero. De Officiis. Translated by Walter Miller. Loeb Edition. Cambridge: Harvard University Press, 1913. http://www.stoics.com