In The Encyclopedia of Diderot and D'Alembert:
Speculative and practical aspects of an art (Diderot):
From the preceding it is evident that every art has its speculative and its practical aspect: the former consists in knowing the principles of an art, without their being applied, the latter in their habitual and unthinking application. It is difficult if not impossible to go far in the practice of an art without speculation, and, conversely, to have a thorough knowledge of the speculative aspects of an art without being versed in its practice. In every art there are many particulars concerning its material, its instruments, and its application which can only be learned through practice. It is the function of practice to present difficulties and phenomena, while speculation must explain the phenomena and solve the difficulties. Consequently, only an artist who can think logically can talk well about his art.
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Diderot, in The Salon of 1765:
"I collected the verdicts of old men and the thoughts of children, the judgements of men of letters, the opinions of the sophisticates, and the views of the people; and if it sometimes happen that I wound artists, very often it's with weapons they themselves have sharpened for me. I've questioned them and come to understand fine draftsmanship and truth to nature; I've grasped the magic of light and shadow, become familiar with color, and developed a feeling for flesh. On my own I've reflected on what I've seen and heard, and artistic terms such as unity, variety, contrast, symmetry, disposition, composition, character, and expression, so comfortable on my lips but so indistinct in my mind, have taken on clear, fixed meanings.
Oh, my friend, how these arts whose object is the imitation of nature, whether by means of eloquence and poetry in discourse, sound in music, paint and brush in painting, chalk in drawing, chisel and clay in sculpture, burin, stone, and metal in printmaking, bow-drill in precious stone carving, stylus, hammer, and punch in chasing, are tedious, laborious, and difficult arts!" (pp. 3-4)
Edmund Burke, in Enquiry into the Sublime and the Beautiful:
"If I make a drawing of a palace, or a temple, or a landscape, I present a very clear idea of those objects; but then (allowing for the effect of imitation which is something) my picture can at most affect only as the palace, temple, or landscape would have affected in the reality. On the other hand, the most lively and spirited verbal description I can give, raises a very obscure and imperfect idea of such objects; but then it is in my power to raise a stronger emotion by the description than I could do by ht ebest painting." ("The Sublime and the Beautiful": p. 60)
François Boucher, in The Salon of 1765:
"The chalk holder has placed in our hands, at the age of seven or eight years. We begin to draw eyes, mouths, noses, and ears after patterns, then feet and hands. After having crouched over portfolios for a long time, we're placed in front of the Hercules or the Torso, the Gladiator, the Medici Venus, and the Antinous. You can be sure that these masterpieces by Greek artists would no longer excite the jealousy of the masters if they were placed at the mercy of the students' grudges. Then, after having spent entire days and even nights, by lamplight, in front of an immobile, inanimate nature, we're presented with living nature, and suddenly the work of all the preceding years seems reduced to nothing; it's as though one were taking up the chalk fo rthe first time. The eye must be taught to look at nature; and many are those who've never seen it and never will! It's the bane of our existance. After having spent five ot six years in front of the model, we turn to the resources of our own genius, if we have any. Talent doesn't reveal itself in a moment; judgements about one's limitations can't be reached on the basis of forst efforts. How many such efforts there are, successful and unsuccessful! Valuable years slip away before the day arrives when distaste, lassitude, and boredom set in. The student is nineteen or twenty when, the palette having fallen from his hands, he finds himself without profession,without resources, and without moral character: for to be young and have unadorned nature ceaselessly before one's eyes, and yet exercise restraint is impossible." (p.5)