I love the preface of Oscar Wilde's novel, the Picture of Dorian. He said that the art have no moral, can express anything. Every feeling, every thought can inspired art. Also that the art has no purpose, art is the purpose. We do things for art's sake and no the other way. He said as well that the interpretation of art, shows us more about the person who interpreted than from the artist.
He has written this in a difficult moment in his life, he was being judge for writing that book, because he talked about controversial stuff, like homosexuality (it was in the xix century). He had some adventures with some guys, and people, because of that book started to talk about it. So with this preface, he try to say, "hey, art can express anything, I'm not gay, please don't make me go to prison". I like all that context (with much drama lol) and I like the reflection he made about art, it made me think about it.