Virtue? A fig! 'Tis in ourselves that we are thus orthus. Our bodies are our gardens, to the which our willsare gardeners
Iago's main core lies in self-control and motivation -- he believes himself to be a man of simple free will, and unlimited freedom. Unrestrained and in control of the chessboard -- he assumes both the external world and (mistakenly) his internal world are under his control, but they may not be.