In Alfonso de Cartagena’s 'Memoriale virtutum' (1422), María Morrás and Jeremy Lawrance offer a critical edition of an anthology of Aristotle’s Nicomachean Ethics, compiled and significantly altered by the major Castilian intellectual of the day, Bishop Alfonso de Cartagena, and addressed to the heir to the throne of Portugal, Crown Prince Duarte. The work is a speculum principis, an education of a future king in the virtues suitable to a statesman. Cartagena’s choice of Aristotle was a harbinger of Renaissance ideas. The “memorial” sheds light on a society in transition, setting new ethical guidelines for the ruling class at the crossroads between medieval feudalism and Renaissance absolutism.