the Incarnation

Invocat te, Domine, fides mea quam dedisti mihi, quam inspirasti mihi per humanitatem Filii tui, per ministerium praedicatoris tui. (Aug. Conf. 1.1)

It was an act of divine courtesy.

development

There is a sense in which the doctrine of the Incarnation stands behind the doctrine of the Atonement; that is, if you bring the truth of Atonement before your contemplation, you will be led to acknowledge the truth of the Incarnation, for the sacrifice of a perfectly just man - who was also only a man - could not atone for anyone but himself.