The power of the good itself spreads further than the power of being; for formless matter and privation and flux aren't said "to be", for being comes through form and they are devoid of form. Yet they are in a way said to be good, in so far as they tend towards act and towards the good, because of some power instilled in them by the good. Therefore, when you say "the good itself", you must mean the good alone, not a good body, or good soul, or intelligence, life, essence, or good being. For you stain the good's purity by mixing it; you reduce its integrity by a subject; you refuse its fulness by adding to it. So do away with this good or that good, as Augustine tells you in the On the Trinity and accept the good which is the good of all good, and you will know what God is. As Dionysius says in the On the Mystical Theology, we can't reach Him by affirmation. For whatever we affirm about Him has been conceived in intelligence, therefore it is something peculiar to us and limited. Therefore God is exalted above every concept. So what He is not we can find out by negation; and how He acts and how others exist with regard to Him we find out by analogy. But what God is is a secret.
"QUID VERO SIT LATET."
-Marsilio Ficino. The Philebus Commentary, translated by Michael J.B. Allen