Much emphasis has been placed on humanity’s pursuit of perfection and progress. Arguably, it has culminated in modern times as a belief in secular humanism — that man can be perfected of his own means without God. In fact, even many Christians would take a subjective viewpoint and argue that God exists because man needs Him. This is false and inverted for it is were true, then Nietzsche would be correct in saying that “God is dead and we have killed Him” since He would only exist drawn out from our need of him; eliminate the need, eliminate the subjective God that man created. In the Catholic culture, this has led some to quote St. Irenaeus’s “the Glory of God is man fully alive.” They leave off, however, that which completes the quote and points towards our utter dependence on God. St. Irenaeus’s quote in full is “the Glory of God is man fully alive, but man fully alive is man when he sees God.”
The Vision of God, the end of man, is what all men are called to. In fact, there lies in man a natural desire to see God. This natural desire to see God has caused many to propose dangerous and even heretical positions. Primarily, the problematic solutions focus on the natural desire to see God as a desire of the will, or a moral desire. Cajetan, so as to avoid the conclusion that God must give man grace (which would result if the natural desire to see God was a moral desire), proposed a hypothetical state of pure nature in which men would be happy without seeing God and receiving grace. Such solution created two ends for man’s nature — a solution incompatible with the faith and St. Thomas Aquinas.
More recently, Henri de Lubac rightly criticized Cajetan’s solution, but de Lubac’s solution created an “individual concretized essence” which is not philosophically sound and “shows a strange nominalism and voluntarism.” Karl Rahner carried de Lubac’s thought further and proposed a “remainder concept” or “Restbegriff”. Such a solution destroys nature for “in the modern authors, there is no real nature to raise as a whole.”
The true solution to the problem revolves around the fact that the natural desire to see God is an intellectual desire, not a moral desire. This is very clear from St. Thomas’s work. St. Thomas examines where man’s beatitude lies for where man’s happiness lies is where too lies his ultimate end. He states, “that knowledge of God which, when acquired, leaves no knowledge of a knowable object to be desired is essentially this (ultimate) felicity.”
Simply knowing God as the first cause, like the philosophers did, does not suffice to satisfy this desire since knowing that God exists, only draws a deeper desire in us to know Him as He is. Our ultimate end cannot be attained philosophically from either natural knowledge like the first cause or the natural capacity for God nor through in-depth philosophical demonstration like the pagan philosophers.
Further, the contemplation of faith does not satisfy the natural desire to see God for “the knowledge of God gained from faith ‘does not put this desire to rest but rather sets it aflame, since every man desires to see what he believes.'” Through faith, we believe what we cannot yet see. That natural desire to see God, a desire in the intellect, cannot be satisfied with belief, but only with seeing the Vision of God.
St. Thomas concludes his examination on the natural desire to see God by asking whether the angels would be satisfied in their desire by “only knowing God through His effects which in their case is their own nature.” Through a series of questions, he concludes, “It is impossible for the natural desire in separated substances [the angels and our souls after death] to come to rest in such a knowledge of God.”(SCG, III, 50)
Therefore, in this life, the natural desire to see God cannot be fulfilled. Indeed, one cannot attain the Vision of God by his own powers even in the next life, but only by grace. Man must be elevated to his ultimate end, and end he was made for and naturally inclined to, by supernatural grace. Only arriving at the Vision of God fulfills mans nature and satisfies man’s intellect.
We can see then that grace perfects nature for “man is called to an end by nature (the Vision of God) that he cannot attain by nature, but only by grace because of the exalted character of the end.” The Catechism confirms this as it speaks of man as naturally capable of God.
“The desire for God is written in the human heart because man is created by God and for God; and God never ceases to draw man to Himself.”
With all this and with all that man is capable of, man still does not add anything to God, but man does demonstrate God’s Goodness. This is why St. Irenaeus can say “the Glory of God is man fully alive.” But to be fully alive, man must be granted perfection through grace that is always freely given by God. Grace that doesn’t destroy nature, but perfects it for man needs grace to attain His end since man “is called to and end by nature that he cannot attain by nature, but only by grace because of the exalted character of the end.” And this is why St. Irenaeus concludes his quote by reminding us, especially modern man who so relies on his own self, that “man fully alive is man when he sees God” — for man, to truly live is only when the natural desire in man’s intellect to know God is attained.
 Fr. Mullady. Lesson 1: The Natural Desire to See God – History. Holy Apostles College and Seminary. 2017.
 Fr. Mullady. Lesson 2: The Natural Desire to See God – Solution. HACS. 2017.
 cf. Summa Contra Gentiles III.
 SCG, III, 39
 Fr. Mullady. Lesson 2. HACS. 2017. p.2
 Fr. Mullady. Lesson 2. HACS 2017
 Catechism of the Catholic Church. p 27.