Aeneas Silvius Piccolomini, de Educatione Liberorum VI:
“Few, however, will be found who are naturally unteachable. For, as Quintilian notes, just as birds are born for flying, horses for running, and beasts for savagery, so are mental agitation and intelligence the natural qualities of humanity. Lazy and unteachable people are no more natural than the giant and remarkable bodies of monsters. Although one person might supercede another in intellect, no one can be found who has not engaged in some pursuit with zeal.”
Pauci tamen reperiuntur quibus natura indocilis est. Sicut enim aves ad volatum (Quintilianus ait), equi ad cursum, ad saevitiam ferae gignuntur, sic hominis propria est agitatio mentis atque solertia; hebetes vero et indociles non magis secundum naturam quam prodigiosa corpora et insignia monstris eduntur. Et quamvis alius alium praestet ingenio, nemo tamen reperitur qui nihil sit studio consecutus.