Aestheticism is a nineteenth-century movement that advocates "art, for the sake of art" and beauty for the sake of beauty.
Essentially, morality and education are pushed aside, and human creativity is given full liberty of expression. No longer will art portray emotion or morals; no longer will it be used to convey the importance of religion or to remind us of saints, nature, or even God. Art is used to feed the senses and to take creativity to the next level.
Keep in mind that this was a radical way of thinking in the Victorian era. These were times when people bought into the philosophies of domestic virtuosity that Queen Victoria so avidly proposed. All aspects of life were to have a backdrop of morality. Therefore, for someone to create something without a "purpose" or without a "rationale" behind it, just for the sake of satisfaction, would have seem hedonistic.
Speaking of hedonism, that is precisely the main influence that fuels the themes and characters in the writings of Joris-Karl Huyssman with À rebours (Against the Grain) and, as a consequence, in Oscar Wilde's The Picture of Dorian Gray. Wilde was quite taken with À rebours, and he mirrored his fascination for the novel in his main character. In fact, Dorian Gray may have been entirely inspired by À rebours; at least we know that Dorian was indeed fascinated enough to live his life by the book, although Wilde never exposes the title of the book that changes Dorian forever.
We learn all about this in chapter 10. Those of us who have read À rebours know that Wilde is referring to this book when he writes,
It was a novel without a plot and with only one character, being, indeed, simply a psychological study of a certain young Parisian who spent his life trying to realize in the nineteenth century all the passions and modes of thought that belonged to every century except his own . . .
There is the evidence of hedonism and how this one young Parisian, Jean Des Esseintes, decides to go for it and explore passion and expression to the highest degree.
We learn Des Esseintes is rich enough to fulfill every desire he wants. He can go as high or as low as he wishes when it comes to experiencing "pleasure." Dorian Gray engages in behaviors very similar to those of Des Esseintes. As such, both characters suffer similar fates. Des Esseintes's life becomes ruined by bad health, genetic illnesses, and an overall rotting of the body. In contrast, Dorian Gray's body remains intact, and it is his soul that becomes putrid, only finally transferring back to his body when the picture that granted Dorian eternal youth is finally destroyed.
In the end, both men end up suffering due to an extreme exposure to passions and pleasures. Still, this is the legacy of these novels: they expose the nature of the "new hedonism" that Lord Henry Wotton talks about, how that hedonism fascinates people, and how some people die to experience every pleasure in life for the sake of pleasure.
Again, that was a wild way of thinking and viewing life for the times. Still, it was influential enough to produce two of the most memorable writings of the era, with À rebours being the key source of inspiration for Dorian Gray.