Goethe’s Tasso, a work so full of finished poetry and of charm, is the idealised and pathetic version of the figure that Diderot has thus conceived for genius. The dialogues between the hapless poet and Antonio, the man of the world, are a skilful, lofty, and impressive statement of the problem that often vexed Diderot. Goethe sympathised with Antonio’s point of view; he had in his nature so much of the spirit of conduct, of saneness, of the common reason of the world. And in art he was a lover of calm ideals. In Diderot, as our readers by this time know, these things were otherwise.
The essay on Beauty in the Encyclopædia is less fertile than most of Diderot’s contributions to the subject.[60] It contains a careful account of two or three other theories, especially that of Hutcheson. The object is to explain the source of Beauty. Diderot’s own conclusion is that this is to be found in “relations.” Our words for the different shades of the beautiful are expressive of notions (acquired by experience through the senses) of order, proportion, symmetry, unity, and so forth. But, after all, the real question remains unanswered—what makes some relations beautiful, and others not so; and the same objects beautiful to me, and indifferent to you; and the same object beautiful to me to-day, and indifferent or disgusting to me to-morrow? Diderot does, it is true, enumerate twelve sources of such diversity of judgment, in different races, ages, individuals, moods, but their force depends upon the importation into the conception of beauty of some more definite element than the bare idea of relation. Some sentences show that he came very near to the famous theory of Alison, that beauty is only attributed to sounds and sights, where, and because, they recall what is pleasing, sublime, pathetic, and set our ideas and emotions flowing in one of these channels. But he does not get fairly on the track of either Alison’s or any other decisive and marking adjective, with which to qualify his rapports. He wastes some time, moreover, in trying to bring within the four corners of his definition some uses of the terms of beauty, which are really only applied to objects by way of analogy, and are not meant to predicate the beautiful in any literal or scientific sense.
There is no more interesting department of æsthetic inquiry than the relations of the arts to one another, and the nature of the delimitations of the provinces of poetry, painting, sculpture, music. Diderot, from the very beginning of his career, had turned his thoughts to this intricate subject. In his letter on Deaf Mutes (1751) he had stated the problem—to collect the common beauties of poetry, painting, and music; to show their analogies; to explain how the poet, the painter, and the musician render the same image; to seize the fugitive emblems of their expression. Why should a situation that is admirable in a poem become ridiculous in a painting?[61] For instance, what is it that prevents a painter from reproducing the moment when Neptune raises his head above the tossing waters, as he is represented in Virgil:
Interea magno misceri murmure pontum.
Emissamque hiemem sensit Neptunus, et imis
Stagna refusa vadis; graviter commotus, et alto
Prospiciens, summâ placidum caput extulit undâ.
Diderot’s answer to the question is an anticipation of the main position of the famous little book which appeared fifteen years afterwards, and which has been well described as the Organum of æsthetic cultivation. In Laocoön Lessing contends against Spence, the author of Polymetis against Caylus, and others of his contemporaries, that poetry and painting are divided from one another in aim, in effects, in reach, by the limits set upon each by the nature of its own material.[62] So Diderot says that the painter could not seize the Virgilian moment, because a body that is partially immersed in water is disfigured by an effect of refraction, which a faithful painter would be bound to reproduce; because the image of the body could not be seen transparently through the stormy waters, and therefore the god would have the appearance of being decapitated; because it is indispensable, if you would avoid the impression of a surgical amputation, that some visible portion of hidden limbs should be there to inform us of the existence of the rest.[63] He takes another instance, where a description that is admirable in poetry would be insupportable in painting. Who, he asks, could bear upon canvas the sight of Polyphemus grinding between his teeth the bones of one of the companions of Ulysses? Who could see without horror a giant holding a man in his enormous mouth, with blood dripping over his head and breast?
Among the many passages in which Diderot touches on the differences between poetry and painting, none is more just and true than that in which he implores the poet not to attempt description of details: “True taste fastens on one or two characteristics, and leaves the rest to imagination. ’Tis when Armida advances with noble mien in the midst of the ranks of the army of Godfrey, and when the generals begin to look at one another with jealous eyes, that Armida is beautiful to us. It is when Helen passes before the old men of Troy, and they all cry out—it is then that Helen is beautiful. And it is when Ariosto describes Alcina from the crown of her head to the soles of her feet, that notwithstanding the grace, the facility, the soft elegance of his verse, Alcina is not beautiful. He shows me everything; he leaves me nothing to do; he makes me wearied and impatient. If a figure walks, describe to me its carriage and its lightness; I will undertake the rest. If it is stooping, speak to me only of arms and shoulders; I will take all else on myself. If you do more, you confuse the kinds of work; you cease to be a poet, and become a painter or sculptor. One single trait, a great trait; leave the rest to my imagination. That is true taste, great taste.”[64] And then he quotes with admiration Ovid’s line of the goddess of the seas:
Nec brachia longo
Margine terrarum porrexerat Amphitrite.
Quel image! Quels bras! Quel prodigieux mouvement! Quelle figure! and so forth, after Diderot’s manner.
Nobody will compare these detached and fragmentary deliverances with the full and easy mastery which Lessing, in Laocöon and its unfinished supplements, exhibits over the many ramifications of his central idea. We can only notice that Diderot had a foot on the track along which Lessing afterwards made such signal progress. The reader who cares to measure the advantage of Lessing’s more serious and concentrated attention to his subject, may compare the twelfth chapter of Laocöon with Diderot’s criticism on Doyen’s painting of the Battle between Diomede and Aeneas.[65] As we see how near Diderot came to the real and decisive truths of all these matters, and yet how far he remains from the full perception of what a little consecutive study must have revealed to his superior genius, we can only think painfully of his avowal—“I have not the consciousness of having employed the half of my strength: jusqu’à présent je n’ai que baguenaudé.”
On the great art of music Diderot has said little that is worth attending to. Bemetzrieder, a German musician, who taught Diderot’s daughter to play on the clavecin, wrote an elementary book called Lessons on the Clavecin and Principles of Harmony. This is pronounced by the modern teachers to be not less than contemptible. Diderot, however, with his usual boundless good nature, took the trouble to set the book in a series of dialogues, in which teacher, pupil, and a philosopher deal in all kinds of elaborate amenities, and pay one another many compliments. It reminds one of the old Hebrew grammar which is couched in the form of Conversations with a Duchess—“Your Grace having kindly condescended to approve of the plan that I have sketched. All this your Grace probably knows already, but your Grace has probably never attempted,” and so forth.