He held the light up again to the canvas, and examined it. The surface seemed to be quite undisturbed and as he had left it. It was from within, apparently, that the foulness and horror had come. Through some strange quickening of inner life the leprosies of sin were slowly eating the thing away. The rotting of a corpse in a watery grave was not so fearful.

– Oscar Wilde

The Picture of Dorian Gray, Chapter 13. Basil holds up a light to the portrait. The picture is being eaten away by the "leprosies" of Dorian’s sins, as described in a vivid metaphor. Dorian has committed terrible sins – but what was the nature of those sins? Wilde once explained to a critic: "Each man sees his own sin in Dorian Gray. What Dorian Gray’s sins are no one knows. He who finds them has brought them." Many of Dorian’s sins, it is supposed, are of a homosexual nature. Sexual intercourse between men was illegal in England in Wilde’s time, the "crime" being known in law as gross indecency.