I BELIEVE IN JESUS CHRIST, HIS ONLY SON, OUR LORD.
The New Testament and the creeds teach us that Jesus Christ is the Son of God, begotten of the Father. This term “begotten” (or, to put it in more modern English) “fathered” has been understood by some (such as the 4th century Arians) to mean that Christ is less God than the Father, or that he was created, or that there was a time before he came into being. However, it is not so that begetting (or “fathering”) is the same as creating, as C. S. Lewis explains –
“To beget is to become the father of: to create is to make. And the difference is just this. When you beget, you beget something of the same kind as yourself. A man begets human babies, a beaver begets little beavers and a bird begets eggs, which turn into little birds. But when you make, you make something of a different kind from yourself. A bird makes a nest, a beaver builds a dam, a man makes a wireless set – or he may make something more like himself than a wireless set: say a statue. If he’s a clever enough carver he may make a statue which is very like a man indeed. But of course, it’s not a real man; it only looks like one. It can’t breathe or think. It’s not alive.”
Now that’s the first thing to get clear. What God begets is God; just as what man begets is man. What God creates is not God, just as what man makes is not man. (C. S. Lewis, “Beyond Personality”, pp. 12-13)
Since God is eternal, then the one who is fathered by God, being God (as Lewis explains above) is also eternal, being eternally fathered by God.
Now, clearly this is a difficult idea to get our heads round, however, I would argue that in speaking in this way, God is using the image of a human father and his son as the clearest way of expressing his eternal relationship to Jesus Christ, the divine Word of God, in language that we can understand.