"There is no such thing as a moral or an immoral book. Books are well written, or badly written..."See in text(The Preface)
This refers to the aesthetic ideal of Art. Art is not meant to educate or moralize. Writing, as an art form, is meant to inspire. If a book leaves a bad impression upon the reader, it is not due to the topic dealt with, but due to the writer's lack of artistic skill.
"Those who find ugly meanings in beautiful things are corrupt without being charming..."See in text(The Preface)
This is a direct jab at Victorians. Wilde was consistently criticized by prudish Victorians for his effeminate use of the word "charming" to describe things. To be "corrupt without being charming" is a message to his critics, telling them that they are ugly people as it is, with the added insult of the use of the word "charming" yet again. (See Oscar Wilde: his Life and Confessions by Frank Harris).
"Vice and virtue are to the artist materials for an art..."See in text(The Preface)
Vice and Virtue would be the modern "Ying and Yang," or polar opposites. The more extremes an artist can experience, the more artistic experiences the artist can produce.
"To reveal art and conceal the artist is art's aim..."See in text(The Preface)
The true artistic signature, according to Wilde, will stamp itself through the universal recognition of the artist's style, rather than the artist's name.
For example, Wilde's writing style is so recognizable in his comedies of manners that, had he gone anonymous, people would have still recognized him as the author of his plays.
"Diversity of opinion about a work of art shows that the work is new, complex, and vital..."See in text(The Preface)
By "new" Wilde does not refer to "recent," but to something so well-made that, even if it is hundreds of years old, it still inspires discourse and argument. An example is the Mona Lisa.
Wilde described himself as a "lover of the young in everything"; this is why he uses the word "new" almost interchangeably with "worthy," "impressive," and even "beautiful."
"No artist is ever morbid. The artist can express everything..."See in text(The Preface)
Another example of the aesthetic principle of L'Art pour L'Art, Art for Art's sake. Wilde insists that the public should cease to judge Art and, instead, admire it for what it is: a product of a higher emotional, even spiritual, state.
"All art is quite useless. OSCAR WILDE..."See in text(The Preface)
This celebrated and controversial statement embodies the aesthetic ideal that Art should not be used as a conduit of morality, judgement, or condemnation. To Wilde and the aesthetes, art is amoral. It exists merely for its own sake, "L'art pour l'art." Hence, when the word "useless" is applied to this statement it is used in its literary, and not in a contextual, meaning. Art simply is to be admired, not "used."
"How English you are, Basil!..."See in text(Chapter I)
Wilde was an Irishman writing for English audiences. However, he often let his disdain for English culture escape through his characters. This time he refers to the penchant in Victorian England to proclaim virtuosity in self and others.
Contrary to popular misconception, Dorian Gray's character was not inspired by Lord Alfred Douglas, Wilde's most influential lover. Ironically and surprisingly, Douglas fits perfectly the description of Gray. However, Wilde had published this, his only novel, prior to meeting Lord Alfred. Dorian's character may have been inspired by John Gray, an up-and-coming poet quite popular among the aesthetes.