Quintilian, Institutio 1.1.1-3
“It is a false complaint that the faculty of understanding what is taught is granted to only a few, and that most people waste their time and energy due to the slowness of their intellect. Just the opposite: you can find many who have an easy time with thinking, and are ready to learn. Certainly, this is natural for humans, just as birds are born to fly, horses are born to run, and beasts are born for savagery; similarly, the activity and ingenuity of the mind is peculiarly our own.
Slow and ineducable people are no more the product of human nature than are giants and wondrously deformed people, but these have been but few. A proof of this is the fact that the hope of many things shines forth in children: if it passes away with age, it is clear that the fault lay not with human nature, but with our lack of care. One might object, ‘But nevertheless, some people are superior in intellect to others.’ I readily concede that point; but that will do more for some than for others. However, no one will be found who has pursued nothing with effort.”
Falsa enim est querela, paucissimis hominibus vim percipiendi quae tradantur esse concessam, plerosque vero laborem as tempora tarditate ingenii perdere. Nam contra plures reperias et faciles in excogitando et ad discendum promptos. Quippe id est homini naturale, ac sicut aves ad volatum, equi ad cursum, ad saevitiam ferae gignuntur, ita nobis propria est mentis agitatio atque sollertia: unde origo animi caelestis creditur. Hebetes vero et indociles non magis secundum naturam hominis eduntur quam prodigiosa corpora et monstris insignia, sed hi pauci admodum fuerunt. Argumentum, quod in pueris elucet spes plurimorum: quae cum emoritur aetate, manifestum est non naturam defecisse sed curam. “Praestat tamen ingenio alius alium.” Concedo; sed plus efficiet aut minus: nemo reperitur qui sit studio nihil consecutus.