In the book, The Alchemist, why does Coelho open his story with the modified myth of Narcissus?

The story of the Narcissus highlights and illustrates the question of selfishness, a question which is at the center of The Alchemist. Is it possible to pursue one's own personal desires while living a good life? In the case of Santiago, the answer is a resounding yes - making the image of Narcissus (who become a flower through his selfishness) especially apt as an opening to the story.