Objection 1. It seems that the perfections of all things are not in God. For God is simple, as shown above (Question 3, Article 7); whereas the perfections of things are many and diverse. Therefore the perfections of all things are not in God.
Objection 2. Further, opposites cannot coexist. Now the perfections of things are opposed to each other, for each thing is perfected by its specific difference. But the differences by which "genera" are divided, and "species" constituted, are opposed to each other. Therefore because opposites cannot coexist in the same subject, it seems that the perfections of all things are not in God.
Objection 3. Further, a living thing is more perfect than what merely exists; and an intelligent thing than what merely lives. Therefore life is more perfect than existence; and knowledge than life. But the essence of God is existence itself. Therefore He has not the perfections of life, and knowledge, and other similar perfections.
On the contrary, Dionysius says (Div. Nom. v) that "God in His one existence prepossesses all things."
I answer that, All created perfections are in God. Hence He is spoken of as universally perfect, because He lacks not (says the Commentator, Metaph. v) any excellence which may be found in any genus. This may be seen from two considerations.
First, because whatever perfection exists in an effect must be found in the effective cause: either in the same formality, if it is a univocal agent--as when man reproduces man; or in a more eminent degree, if it is an equivocal agent--thus in the sun is the likeness of whatever is generated by the sun's power. Now it is plain that the effect pre-exists virtually in the efficient cause: and although to pre-exist in the potentiality of a material cause is to pre-exist in a more imperfect way, since matter as such is imperfect, and an agent as such is perfect; still to pre-exist virtually in the efficient cause is to pre-exist not in a more imperfect, but in a more perfect way. Since therefore God is the first effective cause of things, the perfections of all things must pre-exist in God in a more eminent way. Dionysius implies the same line of argument by saying of God (Div. Nom. v): "It is not that He is this and not that, but that He is all, as the cause of all."
Secondly, from what has been already proved, God is existence itself, of itself subsistent (3, 4). Consequently, He must contain within Himself the whole perfection of being. For it is clear that if some hot thing has not the whole perfection of heat, this is because heat is not participated in its full perfection; but if this heat were self-subsisting, nothing of the virtue of heat would be wanting to it. Since therefore God is subsisting being itself, nothing of the perfection of being can be wanting to Him. Now all created perfections are included in the perfection of being; for things are perfect, precisely so far as they have being after some fashion. It follows therefore that the perfection of no one thing is wanting to God. This line of argument, too, is implied by Dionysius (Div. Nom. v), when he says that, "God exists not in any single mode, but embraces all being within Himself, absolutely, without limitation, uniformly;" and afterwards he adds that, "He is the very existence to subsisting things."
Reply to Objection 1. Even as the sun (as Dionysius remarks, (Div. Nom. v), while remaining one and shining uniformly, contains within itself first and uniformly the substances of sensible things, and many and diverse qualities; "a fortiori" should all things in a kind of natural unity pre-exist in the cause of all things; and thus things diverse and in themselves opposed to each other, pre-exist in God as one, without injury to His simplicity. This suffices for the Reply to the Second Objection.
Reply to Objection 3. The same Dionysius says (Div. Nom. v) that, although existence is more perfect than life, and life than wisdom, if they are considered as distinguished in idea; nevertheless, a living thing is more perfect than what merely exists, because living things also exist and intelligent things both exist and live. Although therefore existence does not include life and wisdom, because that which participates in existence need not participate in every mode of existence; nevertheless God's existence includes in itself life and wisdom, because nothing of the perfection of being can be wanting to Him who is subsisting being itself.
Source: Summa Theologica (New Advent)