The advent of the New Iconography of the Cardinal Virtues, around the turn of the fifteenth century, heralds a technologically informed vision of human behavior, morality, and intellect. Even before this iconographic commingling of virtues and machines, though, it is possible to track changing conceptions of virtue and cognition – especially princely cognition – by examining representations of the virtues in conduct manuals. Showing a marked Aristotelian influence from the middle of the thirteenth century (as do many other learned genres), mirrors for princes accord an ever more prominent place to Prudence and the related virtue of Sapience (Wisdom). In the corpus of political and pedagogical texts translated into French at the behest of Charles V, the iconography of the virtues, discourses on virtue ethics, and the inorganic metaphor of the intellect as engin converge to precipitate a discussion of political virtue and personal vice, the latter of which is assimilated to oxidation. Mirrors for princes and other treatises on education propose to counteract these corrosive influences, but they cannot always compensate for princely imprudence.

Prudence's Mirrors for Princes

Mirrors for princes, which are conduct manuals addressed to a noble readership, are the most widespread textual vehicle of late medieval political theory. Beginning in earnest with John of Salisbury's mid-twelfth-century Policraticus, such texts’ popularity blossomed in the thirteenth century with a number of mirrors inspired by the newly available Latin translations of Aristotle's Ethics and Politics: Vincent of Beauvais's De eruditione filiorum nobilium and De morali principis institutione, Giles of Rome's De regimine principum, which was translated into French quite early and often, and the pseudo-Aquinas’ De eruditione principum, among others. Vernacular mirrors are presented at the French court from the mid-thirteenth century onward. A greater number of the Latin mirrors were translated into French in the fourteenth century, followed by a flurry of mostly vernacular composition in the fifteenth.