In his essays on Edgar Allen Poe, Charles Baudelaire defined the aesthetics of "decadent" literature, with Poe himself as the exemplar. Here are a some extracts from "New Notes on Edgar Poe", included in Baudelaire as a Literary Critic (ed. Hyslop).
Decadent literature!— Empty words which we often hear fall, with the sonority of a deep yawn, from the mouths of those unenigmatic sphinxes who keep watch before the sacred doors of classical Aesthetics. Each time that the irrefutable oracle resounds, one can be sure that it is about a work more amusing than the Iliad. It is evidently a question of a poem or of a novel, all of whose parts are skillfully designed for surprise,whose style is magnificently embellished, where all the resources of language and prosody are utilized by an impeccable hand. When I hear the anathema boom out—which, I might say in passing, usually falls on some favorite poet—I am always seized with the desire to reply: Do you take me for a barbarian like you and do you believe me capable of amusing myself as dismally as you do? Then grotesque comparisons stir in my brain; it seems to me that two women appear before me: one, a rustic matron, repugnant in her health and virtue, plain and expressionless, in short, owing everything to simple nature; the other, one of those beauties who dominate and oppress one's memory, adding all the eloquence of dress to her profound and original charm, well poised, conscious and queen of herself—with a speaking voice like a well-tuned instrument, and eyes laden with thoughts but revealing only what they wish. I would not hesitate in my choice, and yet there are pedagogical sphinxes who would reproach me for my failure to respect classical honor. —But, putting aside parables, I think it is permissible to ask these wise men if they really understand all the vanity, all the futility of their wisdom. The phrase decadent literature implies that there is a scale of literatures, an infantile, a childish, an adolescent, etc. This term, in other words, supposes something fatal and providential, like an ineluctable decree; and it is altogether unfair to reproach us for fulfilling the mysterious law. All that I can understand in this academic phrase is that it is shameful to obey this law with pleasure and that we are guilty to rejoice in our destiny.—The sun, which a few hours ago overwhelmed everything with its direct white light, is soon going to flood the western horizon with variegated colors. In the play of light of the dying sun certain poetic spirits will find new delights; they will discover there dazzling colonnades, cascades of molten metal, paradises of fire, a sad splendor, the pleasure of regret, all the magic of dreams, all the memories of opium. And indeed the sunset will appear to them like the marvelous allegory of a soul filled with life which descends behind the horizon with a magnificent store of thoughts and dreams.
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There is in man, he says, a mysterious force which modern philosophy does not wish to take into consideration; nevertheless, without this nameless force, without this primordial bent, a host of human actions will remain unexplained, inexplicable. These actions are attractive only because they are bad or dangerous; they possess the fascination of the abyss. This primitive, irresistible force is natural perversity, which makes man constantly and simultaneously a murderer and a suicide, an assassin and a hangman;—for he adds, with a remarkably satanic subtlety, the impossibility of finding an adequate rational motive for certain wicked and perilous actions could lead us to consider them as the result of the suggestions of the Devil, if experience and history did not teach us that God often draws from them the establishment of order and the punishment of scoundrels;—after having used the same scoundrels as accomplices! such is the thought which-, I confess, slips into my mind, an implication as inevitable as it is perfidious. But for the present I wish to consider only the great forgotten truth—the primordial perversity of man—and it is not without a certain satisfaction that I see some vestiges of ancient wisdom return to us from a country from which we did not expect them. It is pleasant to know that some fragments of an old truth are exploded in the faces of all these obsequious flatterers of humanity, of all these humbugs and quacks who repeat in every possible tone of voice: "I am born good, and you too, and all of us are born good!" forgetting, no! pretending to forget, like misguided equalitarians, that we are all born marked for evil!