More from Eric Perl’s book Theophany which so far is unpacking that “being as convertible with intelligibility is such an important idea for platonic thought [that has] disappeared with the rise of nominalism” (as a friend who better understands put it).
Despite differences of expression, the structure of participation, implying at once transcendence and immanence, remains the same in Plato, Plotinus, Proclus, and Dionysius: one and the same term is present in many different things, and as what is the same in all of them (immanent), it is other than and unconditioned by all of them (transcendent).
But if all the determinations of all things are the presence of God in them, then God is not merely “in all things,” as if he were in something other than himself. Rather, God is the whole content of reality, “all things in all things.” God “is all things as cause of all things, and holding together and prepossessing in himself all principles, all limits of all beings.” The various features, characters, or natures, the determinations found in a thing, constitute the entire intelligible content of that thing, all that there is in it for the mind to encounter. And since to be is to be intelligible, they constitute the whole of the thing itself. A being can be nothing but the totality of its intelligible determinations, down to the least details by which it is this particular thing and no other. The divine processions are “in” all things, then, not as contained in something other than themselves, but as constituting their entire content. God is the “cause” of all things, and so subject to all names, therefore, in that the entire intelligible content of all things, and hence the whole of reality, is nothing but the differentiated presence of God.