Objection 1. It would seem that in the present state of life the contemplative life can reach to the vision of the Divine essence. For, as stated in Genesis 32:30, Jacob said: "I have seen God face to face, and my soul has been saved." Now the vision of God's face is the vision of the Divine essence. Therefore it would seem that in the present life one may come, by means of contemplation, to see God in His essence.
Objection 2. Further, Gregory says (Moral. vi, 37) that "contemplative men withdraw within themselves in order to explore spiritual things, nor do they ever carry with them the shadows of things corporeal, or if these follow them they prudently drive them away: but being desirous of seeing the incomprehensible light, they suppress all the images of their limited comprehension, and through longing to reach what is above them, they overcome that which they are." Now man is not hindered from seeing the Divine essence, which is the incomprehensible light, save by the necessity of turning to corporeal phantasms. Therefore it would seem that the contemplation of the present life can extend to the vision of the incomprehensible light in its essence.
Objection 3. Further, Gregory says (Dial. ii, 35): "All creatures are small to the soul that sees its Creator: wherefore when the man of God," the blessed Benedict, to wit, "saw a fiery globe in the tower and angels returning to heaven, without doubt he could only see such things by the light of God." Now the blessed Benedict was still in this life. Therefore the contemplation of the present life can extend to the vision of the essence of God.
On the contrary, Gregory says (Hom. xiv in Ezech.): "As long as we live in this mortal flesh, no one reaches such a height of contemplation as to fix the eyes of his mind on the ray itself of incomprehensible light."
I answer that, As Augustine says (Gen. ad lit. xii, 27), "no one seeing God lives this mortal life wherein the bodily senses have their play: and unless in some way he depart this life, whether by going altogether out of his body, or by withdrawing from his carnal senses, he is not caught up into that vision." This has been carefully discussed above (175, 4 and 5), where we spoke of rapture, and in I, 12, 2, where we treated of the vision of God.
Accordingly we must state that one may be in this life in two ways. First, with regard to act, that is to say by actually making use of the bodily senses, and thus contemplation in the present life can nowise attain to the vision of God's essence. Secondly, one may be in this life potentially and not with regard to act, that is to say, when the soul is united to the mortal body as its form, yet so as to make use neither of the bodily senses, nor even of the imagination, as happens in rapture; and in this way the contemplation of the present life can attain to the vision of the Divine essence. Consequently the highest degree of contemplation in the present life is that which Paul had in rapture, whereby he was in a middle state between the present life and the life to come.
Reply to Objection 1. As Dionysius says (Ep. i ad Caium. Monach.), "if anyone seeing God, understood what he saw, he saw not God Himself, but something belonging to God." And Gregory says (Hom. xiv in Ezech.): "By no means is God seen now in His glory; but the soul sees something of lower degree, and is thereby refreshed so that afterwards it may attain to the glory of vision." Accordingly the words of Jacob, "I saw God face to face" do not imply that he saw God's essence, but that he saw some shape [Cf. I, 12, 11, ad 1, imaginary of course, wherein God spoke to him. Or, "since we know a man by his face, by the face of God he signified his knowledge of Him," according to a gloss of Gregory on the same passage.
Reply to Objection 2. In the present state of life human contemplation is impossible without phantasms, because it is connatural to man to see the intelligible species in the phantasms, as the Philosopher states (De Anima iii, 7). Yet intellectual knowledge does not consist in the phantasms themselves, but in our contemplating in them the purity of the intelligible truth: and this not only in natural knowledge, but also in that which we obtain by revelation. For Dionysius says (Coel. Hier. i) that "the Divine glory shows us the angelic hierarchies under certain symbolic figures, and by its power we are brought back to the single ray of light," i.e. to the simple knowledge of the intelligible truth. It is in this sense that we must understand the statement of Gregory that "contemplatives do not carry along with them the shadows of things corporeal," since their contemplation is not fixed on them, but on the consideration of the intelligible truth.
Reply to Objection 3. By these words Gregory does not imply that the blessed Benedict, in that vision, saw God in His essence, but he wishes to show that because "all creatures are small to him that sees God," it follows that all things can easily be seen through the enlightenment of the Divine light. Wherefore he adds: "For however little he may see of the Creator's light, all created things become petty to him."
Source: Summa Theologica (New Advent)