Writing at Reformation 21, Aaron Denlinger recently pointed to Athanasius’s defense of the eternal generation of the Son. Athanasius was of course responding to the arguments of Arius that God the Son must have been created, since fathers always precede sons:
In response to Arius’s argument, Athanasius didn’t shy away at all from the designation of the second person of the Trinity as “Son” or as “begotten.” He simply pointed out, firstly, that human fatherhood is modeled upon divine fatherhood (rather than vice versa): “For God does not make man His pattern; but rather we men, because God is properly, and alone truly, Father of His Son, are also called fathers of our own children.” Thus warning signs are posted along the pathway of attempts to elicit essential truths about the relation of God the Father to God the Son from the relation of human fathers to their sons.
But Athanasius goes further by, secondly, showing how the analogy between divine fatherhood and human fatherhood properly understood (i.e,. in conformity with catholic and biblical Christian truth) actually supports Scripture’s broader identification of the Son as eternal and divine. “If they inquire of parents concerning their son,” he writes, “let them consider … the child which is begotten. For, granting the parent had not a son before his begetting, still, after having him, he had him, not as external or as foreign, but as from himself, and proper to his essence and his exact image, so that the former is beheld in the latter, and the latter is contemplated in the former.” Athanasius’s point is that sons, by the very nature of sonship, share in the nature of their fathers. Like begets like. Humans, who are temporal by nature, beget humans. Despite my younger daughter Geneva’s earnest hope, revealed when asked before Austin’s birth whether she anticipated a brother or sister, that “mommy’s belly” had a “baby puppy” in it, my wife gave birth to a human being last Thursday. Austin was born at a point in time — and so is, by definition, a temporal creature — because his mother and father are themselves temporal creatures who were born at specific points in time.
What human sonship properly implies for non-human sonship, then, is not the temporality of the one born, but the begotten one’s participation in (or possession of) the very same nature as the one who has begotten him. If an eternal (and divine) being begets, then, he necessarily begets an eternal (and divine) being; the begetting of a temporal being by an eternal being would be as implausible as the birth of a “baby puppy” to a daughter of Eve. And if the begotten One is himself eternal (like his Father), then his “birth” cannot have occurred at any moment; that birth itself is eternal (which is precisely what the Nicene Creed affirms).