Quintilian, Institutio Oratoria 1.12:
“Granting that these things should be learned, it is often asked whether they can all be handed over and understood at one time. Some deny it, because the mind is confused at worn out by so many disciplines tending in different directions, for which neither the mind nor the body nor even the day itself is sufficient. Indeed, even if a more robust age could tolerate this, it is hardly right to burden the years of childhood. But these people do not perceive how strong the nature of the human intellect is. It is so agile and swift and looks in every direction, as I have said, so that it is not even capable of doing just one thing, but rather exerts its strength on many things not just on the same day but even in the same instant.
Is it not the case that cithara players attend to memory, the sound of the voice, and many other turns, while at the same time they run over the strings with their right hands, they draw, hold, and release others with their left, while not even the foot is at rest as it preserves the certain order of time. Does this not all happen at the same time?
So? When we are seized by the sudden necessity of doing something, do we not say somethings while thinking ahead about others, at a time when the discovery of the facts, the selection of the words, the composition, gestures, pronunciation, countenance, and motions are all required at once? If people can perform such diverse things in one individual effort, why should we not divide our hours among several cares, especially considering that variety itself tends to restore us, while nothing could be more difficult than to persevere in one task? Therefore, the pen rests during reading and the tedium of reading is alleviated by changes of subject. However many things we may undertake, we are in a certain way always fresh on the scene for whatever we are beginning. Who is there who would not find themselves made full if they had to endure one instructor of any subject for the entire day? The student will be restored by change just as happens in the matter of food, a diversity of which tends to restore the stomach and in many cases nourishes it with less risk of disgust.
Perhaps my detractors should tell me what other mode of learning there might be. Should we sit at the feet of the literature professor only, and then move to the geometer, only to forget in the meantime what we have learned? Should we then shift to music while all of our earlier studies slip away? When we begin to study Latin literature, should we not look back at Greek? And, in short, should we do nothing except for the newest thing? Why do we not persuade the farmers to do the same, and tell them not to simultaneously cultivate grapes and olives and fruits, and not to tend their meadows and flocks and gardens and beehives and birds at the same time? Why do we often give some attention every day to legal matters, to the desires of our friends, to our domestic affairs, to the care of our body, and even to pleasure? Any one of these things, without intermission, would wear us out: so much easier is it to do many things than to do one thing for long.”
Quaeri solet an, etiamsi discenda sint haec, eodem tempore tamen tradi omnia et percipi possint. Negant enim quidam, quia confundatur animus ac fatigetur tot disciplinis in diversum tendentibus, ad quas nec mens nec corpus nec dies ipse sufficiat, et, si maxime patiatur hoc aetas robustior, pueriles annos onerari non oportere. II. Sed non satis perspiciunt quantum natura humani ingenii valeat, quae ita est agilis ac velox, sic in omnem partem, ut ita dixerim, spectat, ut ne possit quidem aliquid agere tantum unum, in plura vero non eodem die modo sed eodem temporis momento vim suam intendat. III. An vero citharoedi non simul et memoriae et sono vocis et plurimis flexibus serviunt, cum interim alios nervos dextra percurrunt, alios laeva trahunt continent praebent, ne pes quidem otiosus certam legem temporum servat – et haec pariter omnia? IV. Quid? nos agendi subita necessitate deprensi nonne alia dicimus alia providemus, cum pariter inventio rerum, electio verborum, compositio gestus pronuntiatio vultus motus desiderentur? Quae si velut sub uno conatu tam diversa parent simul, cur non pluribus curis horas partiamurcum praesertim reficiat animos ac reparet varietas ipsa, contraque sit aliquanto difficilius in labore uno perseverare? Ideo et stilus lectione requiescit et ipsius lectionis taedium vicibus levatur; V. quamlibet multa egerimus, quodam tamen modo recentes sumus ad id quod incipimus. Quis non optundi possit si per totum diem cuiuscumque artis unum magistrum ferat? Mutatione recreabitur sicut in cibis, quorum diversitate reficitur stomachus et pluribus minore fastidio alitur. VI. Aut dicant isti mihi quae sit alia ratio discendi. Grammatico soli deserviamus, deinde geometrae tantum, omittamus interim quod didicimus? mox transeamus ad musicum, excidant priora? Et cum Latinis studebimus litteris, non respiciamus ad Graecas? Et, ut semel finiam, nihil faciamus nisi novissimum? VII. cur non idem suademus agricolis, ne arva simul et vineta et oleas et arbustum colant? ne pratis et pecoribus et hortis et alvearibus avibusque accommodent curam? cur ipsi aliquid forensibus negotiis, aliquid desideriis amicorum, aliquid rationibus domesticis, aliquid curae corporis, nonnihil voluptatibus cotidie damus? Quarum nos una res quaelibet nihil intermittentis fatigaret: adeo facilius est multa facere quam diu.