Hankey on Thomas and Dionysius (Denys)

Thomas has a good sense for the Procline developments reaching from Denys, that is from Greek Christianity, on the one hand, and from the Liber de causis, that is from Arabic Islam, on the other. His knowledge of these developments became more and more exact as his life went on and the texts available to him increased. He recognizes that these Platonists name God being, not absolutely, but in respect to creation, insofar as the first and most proper effect of God in things is their substantial esse. By this, God gives created things a participation in Himself. They imitate God in having an existence of their own. (cxxii)

In differing from Denys, Aquinas recognised how much he owed him. If Rudi te Velde's treatment of the relations between Thomas and Denys be correct, the key to how Thomas will relate participation and substantiality may well have come to him from Denys. [cxxiv]

In Thomas' treatment of the divine intelligence, God is called truth. God is named truth because of an act of comparison or self-reflection. God compares the divine ideas with creatures totally existing by a caused imitation of the divine being as idea.[cxxvii] God is the truth of things so far as their substantial being in its particular grade and character is a participation in divine being, not absolutely, but as thus imitable and imitated.

Underlying is the Iamblichan - Procline notion that, between the unparticipated and the participating, a middle must occur. This becomes, for Denys in this context, the idea that creatures cannot participate the divine being directly, but instead participate its likeness. In Thomas a divine self-reflexive activity is involved to a degree Denys would have found difficult and a pagan Platonist impossible. Thus, Thomas can far more resolutely predicate being of God than Denys or Porphyry can.

-Denys and Aquinas: Antimodern Cold and Postmodern Hot