Aeneas Silvius Piccolomini, de Liberorum Educatione IV:
“The study of literature offers a great aid to attaining virtue, and this befits no one more than a king. With this understanding, the Roman Emperor sent a letter to the king of the Franks, with whom he was then joined in friendship, in which he urged him to have his children brought up in the study of letters, and in which he claimed that an illiterate king was no more than an ass with a crown. I find that the Roman emperors were themselves not uneducated when the empire was at its height; then, learning prevailed in both the senate and the army. Yet it is obvious to all that, once learning was abandoned, all virtues fell into decay, because the strength of the military and the imperial office were weakened as though cut at the root. Indeed, Socrates – as is related by Boethius – used to think that republics were fortunate if it should chance that their rulers were caught up in the pursuit of wisdom, because only those people are perfect, who wish to mix civil business with philosophy and who earn themselves a double good; for, their lives serve the public interest, and is spent in the greatest tranquillity, disturbed by no troubles, engaged in the pursuit of wisdom. Therefore, princes and all those who are to reign should strive with the utmost effort that they both perform their public duties and engage in philosophy, as much as will seem fitting for the times.”
Ad virtutem autem capessendam litterarum studia plurimum adiumenti praebent, nec cuiquam magis quam regi doctrina congruit. Quod intelligens Romanus imperator Francorum regi, quocum tunc amicitia iunctus erat, per epistulam magnopere suadebat, liberos uti suos litteris erudiri curaret, illiteratumque regem quasi coronatum asinum esse dicebat. Nec ego Romanorum principes, dum res publica floruit, illiteratos esse comperi, sed domi atque militiae, et in senatu et in exercitu dominatam esse doctrinam; manifestumque omnibus est, postquam exclusae sunt litterae, omnes elanguisse virtutes. Nam et armatae quoque militiae infirmata est manus et ipsius principatus quasi praecisa radix. Socrates quidem, ut est a Boethio relatum, fortunatas esse res publicas opinabatur, si rectores earum studere sapientiae contigisset. Soli namque perfecti sunt homines, qui civiles cum philosophia partes quaerunt immiscere sibique gemina vendicant bona, nam et eorum vita communi servit utilitati et summa cum tranquillitate nullis obiecta fluctibus per sapientiae studia versatur. Principibus igitur et qui regnaturi sunt experiundum est totis viribus, ut et publica conficiantur negotia et philosophia vendicetur, quemadmodum pro temporibus attinere videbitur.