It may be felt that such doctrines make Dionysius into a mere “monist” or “pantheist.” God, he insists, is not something other than the world but is “all things in all things.” Again, if being is nothing but theophany, does this not imply that the world is not real at all, but only appearance? Such objections, however, represent a failure to understand the Neoplatonic metaphysics of manifestation and intelligibility. Dionysius’ metaphysics is not a form of “pantheism,” if by this we mean the doctrine that all things are God. On the contrary: every being, precisely in that it is a being, i.e. something distinct, ﬁnite, and intelligible, ipsofacto is not God. Indeed, since to be is to be intelligible and therefore to be ﬁnite, to be means to be not God. This, again, is precisely why God is beyond being. Every being, then, absolutely is not God. Nor are all things, taken as a totality, God, for “all things” is plural, a multiplicity of distinct intelligible beings. The God of Dionysius is “all beings and none of beings,” “all things in all things and nothing in any,” and in these formulas the “all” can never be separated from the “none.” As all things without distinction, God is neither any one thing nor all things in their plurality. All things, qua all things, the whole of reality, are absolutely other than God.Eric Perl in Theophany: The Neoplatonic Philosophy of Dionysius the Areopagite
But if Dionysius is not a monist or pantheist, neither is he a dualist, regarding God as another being over against the world. All things are not God, but God is not therefore something else besides all things. Such a notion, as the very words indicate, is manifest nonsense. If God were another being besides his products, he would be included as a member of a more inclusive totality, subordinated to a more embracing universal term, and distinct from the other members and therefore ﬁnite. If God were merely other than the world, he would be another thing and so not truly transcendent, but contained in the world. All things are other than God, but God is not other than all things. Since all things are not God, Dionysius is not a monist; but since God is not something else besides all things, neither is he a dualist.
Dionysius, like his fellow Neoplatonists, is able to negotiate a way between monism and dualism by means of the Platonic concept of appearance, taken up into the doctrine of being as theophany. The relation between an appearance and that of which it is an appearance is not a relation between two beings: the appearance is not another being, additional to that which is appearing. But in that the appearance, qua appearance, is not that which is appearing itself, neither is this a monistic reduction of the appearance to what is appearing. As Plato says, with reference to the status of sensibles as appearances of the forms, they are not being itself, the forms, but neither are they non-being, or nothing. The appearances both are and are not the reality; they are “in between“ being and non-being. So, for Dionysius, beings are not additional things other than God, in such a way that God and the world would constitute two things. But neither are they nothing, or illusion, as in a monist philosophy. Wherever we look, we are not seeing God, in that every being, every object of thought, is not God; and wherever we look, we are seeing God, as he appears, for every being, every object of thought, is nothing but a presentation or appearance of God.
To say that the world is the manifestation or appearance of God, then, is not to say that it is not real. Rather, Dionysius’ Neoplatonic point is that reality itself is appearance: to be real means to be intelligible, to be given to thought, and thus to be appearance. To go beyond appearance, in this sense of what is given to thought, is to go beyond being. As Dionysius’ Neoplatonic metaphysics is neither theism nor atheism, so also it is neither monism nor dualism, but can only be called, for want of a better term, “theophanism.” The relation between appearance and that which appears is irreducible to either unity or duality and cannot be expressed in any terms other than those of appearance, manifestation, image, expression. Only through this Platonic concept is it possible to understand Dionysius’ metaphysics or to make sense of the relation between the world and God without reducing the world to God (monism) or God to a being (dualism).