Irish civilization, wrote James Joyce, is a vast fabric in which it is useless to look for a thread that may have remained pure and virgin without having undergone the influence of a neighbouring thread.  This is also true of literature, and should be remembered whenever one has the temptation of evaluating a literary work from the point of view of originality versus imitation, as in the case of Wildes The Picture of Dorian Gray. Since its publication until very recently the novel has been unfairly referred to by some critics as an imitation or borrowing of different sources as Arnold, Poe, Huysmans, Rossetti, Stevenson, Gautier and Pater, leaving, it seems, little left of Wilde himself. (Mario Praz, not only called him a passive imitator, but placed Dorian Gray in the French School as a curious exotic reflection of it) 
Though Dorian Gray is a very significant thread in the fabric of European decadent limestone, it has no single sources, nor is it a mixture, of works of the period. In one level, it interacts with other European threads reflecting the aesthetics of the moment; but it is unique, in a second level, as an original manifestation of the cultural atmosphere of the nineteenth century as it was drawing to a close. Let us then outline, although briefly, some of the important novels of the eighties and nineties in order m enhance similarities and above all, differences, among them.
Walter Paters Marius, the Epicurean (1885) portrays a philosophic journey in those charmed moments towards the crisis of the second century. Marius, a deeply religious boy, lives in the country-house where his family has dwelt for generations, and where the little gods in their altars receive a few violets, a cake dipped in wine, or morsel of honeycomb. More given in contemplation than to action, as he grows older, an overtension of the soul brings an appetite for adventure, for new experiences whether physical or spiritual. His journey as a pilgrim towards Rome begins, as he says, in search of perfection. In his conversations and long meditations he yearns to grasp the essence of a whole philosophical tradition, beginning with the theory of pleasure. The movements of his thoughts can be followed in the dialogue with Lucian, in which he asks if there are many ways to true philosophy and if each is different from the other, how to choose? How to know that in the door you have entered truth is?
Mariuss journey draws to an end after his visit to his old house, and the tombs of his ancestors, when he is aware that he is the last of a race, that religion of Numa and the old world belong to a past which cannot be recovered. At this moment of despair he finds solace for the disease, of the spirit, as he calls it, in the contact with the Christians, a small group of people who have a strange, new hope, and for whom the ideas of peace, chastity and cheerfulness are a turning-point in his journey. As a primitive Christian, about to die, he receives the last rites, the oil applied to all those passage-ways of the senses, through which the world had come and gone for him. 
In Paters novel, the idea of the end of an era and its consequences on religion, culture, philosophy and language establishes a parallel between the crumbling of the British Empire and that of the Romans, when the old and the new values coexist.
The same sense of vacuity and decline resulted in À Rebours (1884), by J.K. Huysmans,  with a different view of life, though. Des Esseintes, a neurotic young man, also the last of a race, restless and bored with his corrupt life, full of all sorts of perverse, sensuous pleasure, moves in his country-house. In Fontenay-aux-Roses, isolated from humanity, for whom be feels strong aversion, immersed in silence, surrounded by strange paintings and sacred objects used in a profane way, reading decadent Latin writers, literature of sacrilege and Satanism, the objects of his devotion being Baudelaire, Poe and Aurevilly, Des Esseintes goes through an adventure of new, exotic, sensuous, unnatural experiences with colours, shapes, sounds, perfumes, flowers, food and drink. Through imagination he recreates reality artificially. The artifice, as opposed in nature is, for him, the true mark of human genius. His dining-room, for example, is decorated as cabin in a ship. Staring at mechanical fish, made of precious stones, while they swim in an aquarium, and get entangled in artificial vegetation, he admires the flowers, natural, but which imitate the texture and colour of artificial ones.
In the end, awful nightmares, the use of drugs and very painful physical suffering almost drive him mad; he is forced to go back to Paris, a Roderick Usher well-versed in the writings of Sade.
Marius and Esseintes: two journeys, but how different. Pleasure, for Marius, is fullness of life, and insight - as conducing to that fullness - energy, variety, and choice of experience, including noble pain and sorrow even.  In Rome, his  vacuity of spirit ends with the idea of Humanism while Des Esseintes aversion for the human face will be his main torture in Paris.
Other decadent heroes have been anxious to extract pleasure from every moment, as young Count Andrea Sperelli, poet and painter, in DAnnunzios Il Piacere (1889) which begins with the death of the year, lanno moriva, assai dolcemente, in reference to the end of an affair, but also to the end of century. Sperelli, the last of a noble Italian intellectual race, received an aesthetic education under the guidance of his father who had a certain Byronic inclination for fantastic romanticism. His precept was Bisogna fare la propria vita, come si fa un opera darte. 
Sperellis aristocratic, refined tastes, and cult of Beauty, build, as he likes to think, the scenery for the comedy of love with the pleasures of the flesh: expensive carpets, valuable pieces of furniture brought from old churches, erotic paintings, splendid roses, objects dart, create an atmosphere of voluptuousness in which passion is so intense that it becomes one with the idea of death: Moriremo, Elena Must whispers many times.
Sperelli, however, seriously hurt in a duel, spends some time recovering in the country. There he meets Maria, a sensitive, loving mother, whose splendor of the spirit contrasts sharply with the gallery of sensual women he had known. The paintings in this part of the novel reflect the change in Sperelli (the Madonna, Nativity, Annunciation). Despising vice, his conversations with Maria are about the soul, about music, and the beauty of nature, so different from the air of corruption of his house in Trinitá del Monti. But in autumn Sperelli finds himself in Rome again, only to dive into pleasure more intense than before, dreading to think that life is but a dream.
Valle Incláns Sonata de Ontoño - Memorial del Marquis de Bradomín (1902) [Autumn Sonata - Memories of the Marquis of Bradomin] goes deeper into the theme of time that destroys every moment, inexorably. Its autumn, Concha is dying; she asks her lover to visit her for the last time: Mi amor adorado! Estoy muriendo y solo deseo verte, establishes the theme of love and death In the old palace, Concha and the Marqués de Bradomín, the last of their lineage, re-enact the passionate scenes of years ago. As a married woman, and also his cousin, their sense of guilt bad become too strong; they had parted Was their great sin adultery? Or incest?
While staring at the pallid beauty of his dying lover, her face Re that of a Mater Dolorosa, her hands of eucharistic whiteness, her languid pallid lips that bite his lips, the soul of the Marqu6s is drunken with the perfume of a sick rose. Every detail in the palace is invested with symbolic meaning, as the white pigeons and the black bird, the fountain, the labyrinth, the moon, the clock, the roses destroyed by the rain: Era noche de luna, y en el fordo del laberinto cantaba la fuente como un pájaro escondido. 
In a cadenced prose of great beauty, Sonata de Ontoño is, among the novels briefly discussed, one in which Poes inspiration is most strongly felt. It would fit in the Romantic Agony, by Mario Pisa, whose focus is on the erotic sensibility of decadent literature.
Five great novels, five varieties of one literary moment. They share, of course, common traits; the hero, for example: a young, neurotic, aristocratic, refined character who makes art his religion, and goes through self-awareness and self-analysis, torn between the flesh and the spirit in search of pleasure, beauty and truth. The novels show common themes as well: the urgency of time, a sense of cultural saturation, weariness and degeneration in the twilight of an era (here we are reminded of Yeatss essay Autumn of the Body). But these common traits, and others, do not take from the novels discussed their deeper level of significance. The theme of specular reflexion, for example, in Dorian Gray and in Wildes prose poem, The Disciple, is also used by André Gide in Le Traité de Narcisse (1891) - the same myth under a new form, an expression used in a letter by Wilde about Dorian Gray. He writes: the idea of a young man selling his soul in exchange for eternal youth - an idea that is old in the history of literature, but to which I have given new form. 
Rewriting has always been a very important device in literature; but never, I think, has it been used as frequently as in the twentieth century when the Odyssey, Jane Eyre, Hamlet, the plays of Euripides and Sophocles, The Tragical History of Dr. Faustus - the list is endless - have become a departure, or frame, for other great works. Wildes idea of a new form, is of course in T. S. Eliots much-quoted Tradition and Individual Talent, or in Harold Blooms Anxiety of Influence.
I hope to have raised a few points about a literary period, the Decadence, which should be seen not as a close-ended phase but as containing anticipatory traits of the modern period. Isobel Murrays suggestion that perhaps Wilde has more in common with some of the Great Modernists than has been hitherto been allowed  - should be taken into consideration in the discussion of Dorian Gray and Wildes critical essays, in which light we see Decadence, as Matei Calinescu does , as one of the five faces of modernity.