There are several ways to go about responding to an issue like this. The most simple and obvious is, of course, to say “Why, God did make his existence as obvious as the moon—in fact, the moon itself is positive evidence for the existence of God: all the world is a testimony to his reality!” Which is, of course, true, as St. Paul told us (Romans 1:20ff). But this is rather ineffective to the atheist. Furthermore, while true, it doesn’t really strike to the core of the question of Christianity, in particular, nor does it explain the inconsistency in the beliefs (specifically about salvation) amongst those who already believe in God. So, where are we as Christians to turn?
I’ve always maintained that all of Christian theology can be summed up in two words: Trinity and Incarnation. Interestingly, enough, it is on these exact two points that the atheists most fail to comprehend the nature of Christian revelation. So, let us ask, why doesn’t God give a universal revelation of himself and make it obvious to everyone? The answer: Incarnation. St. John of the Cross in his Ascent of Mount Carmel said:
Wherefore he that would now enquire of God, or seek any vision or revelation, would not only be acting foolishly, but would be committing an offence against God, by not setting his eyes altogether upon Christ, and seeking no new thing or aught beside. And God might answer him after this manner, saying: If I have spoken all things to thee in My Word, Which is My Son, and I have no other word, what answer can I now make to thee, or what can I reveal to thee which is greater than this? Set thine eyes on Him alone, for in Him I have spoken and revealed to thee all things, and in Him thou shalt find yet more than that which thou askest and desirest. For thou askest locutions and revelations, which are the part; but if thou set thine eyes upon Him, thou shalt find the whole; for He is My complete locution and answer, and He is all My vision and all My revelation; so that I have spoken to thee, answered thee, declared to thee and revealed to thee, in giving Him to thee as thy brother, companion and master, as ransom and prize.
So, as Christians, we declare that Christ is the definitive revelation of God and all things are contained in him. There is no need or desire for further revelation because everything rests in the sacred heart of Jesus, the Christ. After all, what more could God possibly reveal about himself than the person of himself, in the flesh, walking amongst us, no longer communicating with mere words, riddles or dreams, but speaking to us face to face, as with friends?
But the atheist is still unsatisfied with the response. They don’t think that Christ is the best possible revelation because the Incarnation does not—in their minds—meet the criteria of being the most direct means of conveying the knowledge of God and salvation to the broadest number of people. That God has come among us in the flesh, they argue, is not as obvious as the existence of the moon. But since God is omnipotent, he could reveal himself to more people with more uniformity and therefore lead more people to salvation. Since God is supposed to desire the salvation of all men, must it not be the case that God does not exist? The answer: the Trinity.
The interior life of God can always tell us something about God’s relationship with the world. Particularly since this specific question raised by the atheists addresses the salvation of mankind, we must touch upon what salvation is from this perspective. In the interior life of the Trinity love is most perfectly manifest, for God is Love. The Father gives himself completely and freely to the Son, the Son returns himself completely to the Father and the bond of giving and receiving one another is the Holy Spirit—one God composed of three persons in an eternal dance of absolutely self-giving, interpenetrating Love. What does this tell us about salvation and the fittingness of the Incarnation as its definitive expression? The saints have always affirmed that the meaning and purpose of the Incarnation was that men might partake of divinization or, as it is called in the East, theosis. As St. Athanasius said, “God became man so that man might become god.” That is, God wishes to bestow on mankind his divine nature and welcome mankind into the interior life of the Trinity.
With that in mind, we see how fundamentally fitting it is that God should reveal himself definitively through the Incarnation. God wants mankind to partake of the divine nature; that is the definition of salvation. Then God himself likewise takes on human nature. God wants to reveal himself to mankind? Well then, God should invite mankind to be co-workers in that with him as in all things. And that is the reality. Why does God reveal himself in the Incarnation and then Ascend to Heaven, leaving the propagation of the saving message of the divine life in the hands of the Church (a sacramental body of both divine and human elements)? Because, given the nature and meaning of salvation, it simply would not be fitting for it to happen in any other fashion. God wants man as active co-participants in all his works—from the creation of new life in the conception of children, to the redemption from sin by way of the sacraments through his priestly ministers, and the proclamation of the Gospel and the world-wide realization of his saving message is part of that cooperation, a duty and a responsibility incumbent upon all Christians.
So, in short, why doesn’t God simply make a great, world-wide revelation of himself directly to every individual that makes his presence as obvious as the moon? He simply loves you too much to leave you out of the work.