In my experience, one of the principal delights of growing older -- more than adequate compensation for hair loss, aches and pains, and other unpleasantries associated with the art -- is seeing one's family increase through the addition of children (and, presumably, grandchildren, though I'm far from that stage). Last Thursday morning I had the pleasure of holding in my arms for the very first time my newborn son Austin. Austin is our third child, and our first boy (not counting our dog, who bears a striking similarity to me, at least behaviorally, despite our lack of shared genetics).
Children, of course, provide numerous joys (and, to be fair, numerous anxieties). One of the more easily overlooked of those joys, I think, is -- at least for a Christian father -- deeper appreciation for the reality and depth of God's own fatherly love, both as such is realized in the immanent Triune life of God, and as such is realized in God's relationship to believers. Within the inner life of God, after all, there is (eternally) a Father and a Son, and God has revealed himself (in time) as the adoptive Father of those whose salvation has been purposed from eternity and accomplished in time through the Spirit's application to them of the Son's saving work (cf. Matt. 3.17 & Eph. 1.5). Becoming and being an earthly father, I believe, grants experiential insight into God's sentiments toward his adopted children as well as God the Father's sentiments toward his proper Son, and so also experiential insight into the profound sacrifice involved in God the Father's gift of his only-begotten Son for our salvation (John 3.16).
Scripture itself provides us some license to gauge the depth of God's (parental) love for us by taking stock of human (parental) love: "Can a woman forget her nursing child, that she should have no compassion on the son of her womb? Even these may forget, yet I will not forget you" (Isa. 49.15). The truth posited in this verse is of course accessible to all, but the nursing mother will feel the point made in a particular way. Yet, it is possible to get a bit carried away in this regard. It is possible to start thinking God's relationship to his elect children, or even God the Father's relationship to God the Son, is itself somehow modeled upon the earthly phenomenon of fatherhood -- as if human fatherhood (and, correspondingly, human sonship) were the architectural plan to which the relationship between Father and Son in the Godhead must conform, however grander the actual building might be in comparison to the drawing.
The third-century Alexandrian priest Arius got carried away in just this regard, at least in terms of his rhetoric. Arius's basic thesis -- namely, that the Son of God is essentially a creature (rather than the Creator) -- stemmed from other considerations, but in the interest of defending his position, he explicitly appealed to the analogy between divine and human fatherhood. And, apparently, his argument struck a particular chord with certain parents. In his Four Discourses against the Arians, the Alexandrian bishop Athanasius tells us that Arius made it his habit to approach "silly women, and address them in turn in this womanish language: 'Had you a son before bearing? Now, as you had not, so neither was the Son of God before His generation.'" Arius's reasoning, in other words, was that since, say, Austin's birth occurred at a point in time (7:37 a.m. last Thursday, to be precise), and that since prior to his birth (or really conception) Austin was not, God's Son too must have been born (as it were) at some precise moment and, prior to that, not have been per se.
Athanasius reckoned that "words so silly and dull deserve no answer at all." Nevertheless, in addition to marshalling an impressive number of biblical texts and theological arguments in defense of Nicene orthodoxy (which judged the Son "true God from true God, begotten not made, of one substance with the Father"), Athanasius responded to said words, largely out of concern for "the silly women who are so readily deceived by them."
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).
The doctrine of the Son's eternal generation from the Father (and, correspondingly, the Father's eternal generating of the Son) has fallen on hard times of late. Several notable evangelicals have openly rejected the doctrine, suggesting that it lends itself to subordinationism (the position that the Son is ontologically inferior to the Father). Ironically, subordinationism is the very thing the Nicene doctrine of the Son's eternal generation, so well expressed and defended by Athanasius, was intended to subvert. Perhaps better awareness of historic debates surrounding Christianity's historic doctrines -- buttressed if necessary by some personal experience in fatherhood -- would generate (no pun intended) greater reservation in rejecting this and other creedal Christian truths.