Excerpt:

 A large Nativity on a single panel, the canon had said; narrative altarpieces are no longer in fashion. You'll need to come and measure the palace chapel. Or perhaps an Adoration, with shepherds and wise men, if you'd rather, added the canon, but for the same price. Your fee will not be based on the number of horses or camels, but on the way in which you make the incarnation of divinity visible. Christ and sex - right off, the two words seem mutually exclusive. The word sin separates them and keeps them forever at a distance. The former is exempt from it, and the latter is immersed in it. And for precisely that reason, bringing them together in an image would be the strongest and surest way to create surprise and strike the senses.

Read a longer excerpt on The Arts Desk here.