"One of the creeds says that Christ is the Son of God 'begotten, not created'; and it adds 'begotten by his Father before all worlds'."

There have been various creeds in Christendom over the years that have sought to codify a concise yet comprehensive statement of what Christians believe. Here Lewis refers to the Nicene Creed, which states in part, "I believe in one God, the Father Almighty, maker of heaven and earth, and of all things visible and invisible; And in one Lord Jesus Christ, the only begotten Son of God, begotten of his Father before all worlds. . . ." Information on the history of the Nicene Creed may be found here.