The great Irenaeus of Lyons teaches us that the glory of God is a human being fully alive (Adversus haereses 4.20.7). It’s worth meditating on. Consider this: a truly living human being is the glory of God, God’s magnificence, God’s doxa, from Greek, which bears a sense of splendor. As the great Apostolic Tradition of both East and West testifies, this human being fully alive is Christ Incarnate – and all that are in Him (see Ephesians 1-2). It is Christ, but Christ that is Incarnate, Christ the God-Man, Christ who possesses the created, human Sacred Heart that fully lives in and through God.
On the other hand, we might say that the beauty of the human being is the Logos Incarnate. As the Word of God becomes Man, He vivifies and beautifies the very being of ours. He makes us truly alive and puts our being into an order of beauty and harmony, He orders us towards God. Not only He transforms God’s earthly handiwork into God’s glory, but also by His own presence in our human being becomes a gift of beauty. Why do I speak of beauty? You see, for the ancients the Logos was the principle of order and harmony, of the rationality of nature. The Logos made the cosmos – the world – what is was: a beautiful order (that’s the meaning of kosmos in Greek). So in the Gospel that Logos, this divine principle of beauty and harmony which can be perceived throughout nature, is revealed to be a divine person, but even more – that personal Logos becomes a human being. The whole beauty of the cosmos is now densely embodied in Jesus Christ, the Logos Incarnate. He is the glory of God, He is the beauty of Man.
By the way, if you’re looking for a good introduction into the thought of St. Irenaeus of Lyons, I can recommend no better work than Irenaeus of Lyons: Identifying Christianity by John Behr. It is a rigorous scholarly study and a spiritual treasure at the same time – something that we badly need in our days.