It seems an odd thing to say: theotes (Godhead, divinity, deity) does not refer to the divine nature (physis) but to the divine activity (energeia). It’s odd, because that’s not how we use language for most things that we know. It’s as if we were to ask a philosopher “What is a human being?” and he were to respond, “A human being is an animal that eats organic food, spends a third of his life commuting back and forth to work, and watches television in the evening.” After hearing this response, we probably would reply, “I didn’t ask you what a human being does. I want to know what it is.” “But human beings are what they do,” the philosopher responds. And we stand there shaking our heads in perplexity. But let’s let the Nyssen explain his position in his own words:
Most people think that the word ‘Godhead’ refers to God’s nature in a special way. Just as the heaven, the sun, or any other of the world’s elements is denoted by a proper name which signifies its subject, so they say that, in reference to the transcendent and divine nature, the word ‘Godhead’ is fitly applied, like some proper name, to what it represents. We, however, following the suggestions of Holy Scripture, have learned that His nature cannot be named, and is ineffable. We say that every name, whether invented by human custom or handed down by the Scriptures, is indicative of our conceptions of the divine nature, but does not signify what that nature is in itself. … From this it is clear that the divine nature in itself is not signified by any of these terms. For we say, perhaps, that the divine is incorruptible or powerful or whatever else we are in the habit of saying. But in each of these terms we find a particular idea which by thought and expression we rightly attribute to the divine nature, but which does not express what that nature essentially is. For the subject, whatever it may be, is incorruptible, but our idea of incorruptibility is this: that that which is not resolved into decay. In saying, then, that He is incorruptible, we tell what his nature does not suffer. But what that is which does not suffer corruption we have not defined. Or again, even if we say he is the creator of life, while we indicate by the expression what it is he creates, we do not reveal by the word what creates it. By the same principle, we find in all other cases that the significance attaching to divine names lies either in their forbidding wrong conceptions of the divine nature or in their teaching right ones. But they do not contain an explanation of the nature in itself. (Ad Ablabius in Christology of the Later Fathers, pp. 260-261)
The divine names do not define and grasp the divine nature; they do not express what the nature is. We have already briefly addressed this theme in the article on the divine propria. Negative terms tell us what God is not; positive terms specify the essential properties that God has; but whether presented in either negative or positive modality, our language for God does not capture what God is. In his transcendent nature, God remains incomprehensible. Our words point to God but do not define him. This linguistic incapacity issues from the infinitude of the divine nature:
For we believe that the divine nature is unlimited and incomprehensible, and hence we do not conceive of its being comprehended. But we declare that the nature is in every way to be thought of as infinite. What is altogether infinite is not limited in one respect and not in another, but infinity entirely transcends limitation. Therefore that which is without limit is certainly not limited by the word we use for it. In order, then, that our conception of the divine nature should remain unlimited, we say that the divine transcends every name for it. And one of these names is “Godhead.” The same thing, then, cannot on the one hand be identical with the name, and yet on the other be conceived as transcending every name. (p. 264)
It needs to be remembered that Gregory developed his understanding of the ousia of God and the nature of theological language principally in dispute with Eunomianism. Not only did Eunomius claim that we may know the essence of God, and thus can provide a definition for him (namely, God is ingenerate), but his position ultimately dissolved into the assertion of the exclusivity of essential knowledge. As Andrew Radde-Gallwitz phrases it, for Eunomius “God’s essence is all there is to know” (Basil of Caesarea, Gregory of Nyssa, and the Transformation of Divine Simplicity, p. 108). In refutation Gregory avers that infinite being transcends all human conceptuality. God is incomprehensible because he is infinite, and he is infinite because he is the Creator who transcends everything he has made. Luca Francisco Mateo-Seco explains:
Divine infinity also marks the essential and unfathomable difference that exists between the uncreated Being and created being: God is incomprehensible to every created being, precisely because of his infinity. The difficulties in knowing Him are not born of the opposition between matter and spirit, but from the primordial difference that exists between the infinite and that which is finite, uncreated Being and created being. The universe reflects the perfections of the Creator, for example, his Wisdom. Being limited, however, it cannot manifest infinity in itself, i.e. it cannot manifest the divine nature. God is above all limits, every definition and every created word. (Dictionary of Gregory of Nyssa, p. 702).
That which has no boundaries cannot be identified by the stipulation of boundaries. God is not a some-thing. The Gregorian theme of infinity has received a great deal of attention from patristic scholars. Some have asserted that the notion of divine infinity is original to Gregory; others that he inherited the notion, perhaps from Philo or Plotinus, and made it distinctly his own. Anthony Meredith notes that in asserting that God “is the source of all and can be limited by none,” Gregory moves beyond Plato and Origen, both of whom judged “the absence of limit and form as a defect” and thus inappropriate for divinity (Gregory of Nyssa, p. 13). Infinity clarifies and grounds the assertion of divine incomprehensibility. How can we comprehend that which surpasses all creaturely categories and conceptuality? How can we define that which is boundless? “Infinite being,” elaborates Robert W. Jenson, “cannot be something other than its own infinity, for were it something, it would just thereby be marked off from other things and would have a boundary, a finis, which is what ‘infinite’ denies. Just this observation was the occasion of the Greeks’ aversion to infinity: an infinite something would have no spatial shape, no form, and so in their thinking would be nothing at all. ‘Infinite form’ is a Platonic or Aristotelian oxymoron; so also, therefore is ‘infinite deity'” (Systematic Theology, I:215).
St Gregory is emphatic that God is unknowable to creatures: “The divine nature, taken on its own, whatever it is in essence, transcends all comprehensive conceptualization” (Beat. 6). Yet as observed in previous articles in this series, it would be inaccurate to interpret Gregory in terms of a pure apophaticism, as we find, for example, in Clement of Alexandria or Pseudo-Dionysius.
(30 April 2014; mildly edited)