Here's an example of an image that in its day was considered borderline pornographic (the Catholic Cardinal who commissioned it kept it hidden behind a velvet curtain in his Roman Palazzo). Today it is considered part of the Canon of western art, much like Michelangelo's David. Yet you can't call it porn, because it has so many other points of reference beyond the sexual suggestion. There are the referents to classical mythology (Cupid, with his wings and bow), the contemporary symbols of musical instruments with their allusion to performance and education as well as seduction...and the masterful, even revolutionary, understanding of light and shadow, and how to capture them on canvas.