Dorian's physical beauty is his most cherished attribute, and vanity is, as a consequence, his most crippling vice. Once a sense of the preciousness of his own beauty has been instilled in him by Lord Henry, all of Dorian's actions, from his wish for undying youth at the beginning of the novel to his desperate attempt to destroy the portrait at the end, are motivated by vanity. Even his attempts at altruism are driven by a desire to improve the appearance of his soul. Throughout the novel, vanity haunts Dorian, seeming to damn his actions before he even commits them; vanity is his original sin. Dorian's fall from grace, then, is the consequence of his decision to embrace vanity - and indeed, all new and pleasurable feelings - as a virtue, at the behest of Lord Henry, his corrupter. In the preface to the novel, Wilde invites us to ponder the inescapability of vanity in our own relationship to art when he states that "it is the spectator, and not life, that art really mirrors." If we see ourselves in art, and find art to be beautiful, then it follows that we, like Dorian, are in fact admiring our own beauty.
