In the 13th century, the most detailed and extensive European encyclopedias appeared not only in Latin, but also in national languages. The first such encyclopedia that broke with the Latin tradition was the book ‘Li livres dou Tresor’ written in French by the Florentine scholar, writer and politician Brunetto Latini. The second part of this writing contains the moral teaching, namely, knowledge of vices and virtues, according to general opinion, based on the Aristotelian ‘Nicomachean ethics.’ The article measures up the extent to which Brunetto Latini relied on Aristotle’s treatise, whether there were other sources for the ethical part of his encyclopedia, and what impact this work had on the subsequent moral philosophy.