4 But remember thou what was said yesterday concerning His Godhead. Believe that He the Only-begotten Son of God— He Himself was again begotten of a Virgin. Believe the Evangelist John when he says, And the Word was made flesh, and dwelt among us. For the Word is eternal, Begotten of the Father Before All Worlds: but the flesh He took on Him recently for our sake. Many contradict this, and say: “What cause was there so great, for God to come down into humanity? And, is it at all God's nature to hold intercourse with men? And, is it possible for a virgin to bear, without man?” Since then there is much controversy, and the battle has many forms, come, let us by the grace of Christ, and the prayers of those who are present, resolve each question.
Source: Catechetical Lectures (New Advent)