“A natural talent is required; for, when Nature opposes, everything else is in vain; but when Nature leads the way to what is most excellent, instruction in the art takes place, which the student must try to appropriate to himself by reflection, becoming an early pupil in a place well adapted for instruction. He must also bring to the task a love of labor and perseverance, so that the instruction taking root may bring forth proper and abundant fruits.”

Variant translation: We conclude that God is known first through Nature, and then again, more particularly, by doctrine; by Nature in His works, and by doctrine in His revealed word.
Book I, Chapter XVIII.—Notwithstanding Their Conceits, the God of the Marcionites Fails in the Vouchers Both of Created Evidence and of Adequate Revelation.
This was quoted by Galileo in his defense of natural sciences.
Galileo Galilei: Letter to the Grand Duchess Christina of Tuscany, 1615 https://people.bu.edu/dklepper/RN242/duchess.html
Against Marcion https://www.newadvent.org/fathers/0312.htm
Original: (la) Digna enim deo probabunt deum. Nos definimus deum primo natura cognoscendum, deinde doctrina recognoscendum, natura ex operibus, doctrina ex praedicationibus.

Source: Meditations (c. AD 121–180), Book X, 14

the conscience shrieks, in effect, to all the other mental processes. The other processes try it for a while, note that the conscience is unappeased, that it continues to shriek, and they note, too, that the outside world has not been even microscopically improved by the unselfish acts the conscience has demanded. They rebel at last. They pitch the tyrannous conscience down an oubliette, weld shut the manhole cover of that dark dungeon. They can hear the conscience no more. In the sweet silence, the mental processes look about for a new leader, and the leader most prompt to appear whenever the conscience is stilled, Enlightened Self-interest, does appear. Enlightened Self-interest gives them a flag, which they adore on sight. It is essentially the black and white Jolly Roger, with these words written beneath the skull and crossbones, 'The hell with you, Jack, I've got mine!"
God Bless You, Mr. Rosewater (1965)

And he says this not proudly, but obediently and well pleased with her.
X, 14
Meditations (c. 121–180 AD), Book X

Vol. 2 "On Philosophy and the Intellect" as translated in Essays and Aphorisms (1970), as translated by R. J. Hollingdale
Parerga and Paralipomena (1851), Counsels and Maxims
Context: Talent works for money and fame; the motive which moves genius to productivity is, on the other hand, less easy to determine. It isn’t money, for genius seldom gets any. It isn’t fame: fame is too uncertain and, more closely considered, of too little worth. Nor is it strictly for its own pleasure, for the great exertion involved almost outweighs the pleasure. It is rather an instinct of a unique sort by virtue of which the individual possessed of genius is impelled to express what he has seen and felt in enduring works without being conscious of any further motivation. It takes place, by and large, with the same sort of necessity as a tree brings forth fruit, and demands of the world no more than a soil on which the individual can flourish.

Guide for the Perplexed (c. 1190), Introduction
Context: You must know that if a person, who has attained a certain degree of perfection, wishes to impart to others, either orally or in writing, any portion of the knowledge which he has acquired of these subjects, he is utterly unable to be as systematic and explicit as he could be in a science of which the method is well known. The same difficulties which he encountered when investigating the subject for himself will attend him when endeavouring to instruct others: viz., at one time the explanation will appear lucid, at another time, obscure: this property of the subject appears to remain the same both to the advanced scholar and to the beginner. For this reason, great theological scholars gave instruction in all such matters only by means of metaphors and allegories.

The Analects, The Doctrine of the Mean
Context: What Heaven has conferred is called The Nature; an accordance with this nature is called The Path of duty; the regulation of this path is called Instruction. The path may not be left for an instant. If it could be left, it would not be the path. On this account, the superior man does not wait till he sees things, to be cautious, nor till he hears things, to be apprehensive.

Neither natural ability without instruction nor instruction without natural ability can make the perfect artist.
Morris Hicky Morgan translation
Source: De architectura (The Ten Books On Architecture) (~ 15BC), Book I, Chapter I, Sec. 3; translation by Frank Granger

Source: How to Read a Book (1940, 1972), p. 12