Herman Bavinck on the Advent Incarnation

The doctrine of Christ is not the starting point, but it certainly is the central point of the whole system of dogmatics. All other dogmas either prepare for it or are inferred from it. In it, as the heart of dogmatics, pulses the whole of the religious-ethical life of Christianity. It is ‘the mystery of godliness’ (1 Tim. 3:16). From this mystery all Christology has to proceed. If, however, Christ is the incarnate Word, then the incarnation is the central fact of the entire history of the world; then, too, it must have been prepared from before the ages and have its effects throughout eternity…the incarnation is not an incidental decree that emerged later: it was decided and determined from eternity. There was not time when the Son did not exist; there was also no time when the Son did not know he would assume and when he was not prepared to assume the human nature from the fallen race of Adam. The incarnation was prepared from eternity; it does not rest in the essence of God but in the person. It is not a necessity as in pantheism, but neither is it arbitrary or accidental as in Pelagianism.

—Reformed Dogmatics, Vol. 3, pp. 274; 276-277 (found this by way of friend-of-the-blog Austin Ricketts)