In the early 390s St Gregory of Nyssa received a request for counsel on the virtuous life, or as Gregory phrases it: “You requested, dear friend, that we trace in outline for you what the perfect life is” (I.3). His response was the remarkable The Life of Moses, or Concerning Perfection in Virtue (Vita Moysis).
The task, Gregory explains, is more difficult than one might anticipate. Whereas the perfection of every finite object is determined by its delimited nature, “in the case of virtue we have learned from the Apostle that its one limit of perfection is the fact that it has no limit” (I.5). Hence it is impossible for anyone to attain fullness in virtue, for there is always more that may be cultivated, expanded, and acquired. At no point do we hit a barrier that allows us to say, “I have achieved perfection.” Life, as understood by the Nyssen, is self-transcendence, continuous movement toward a goal that can never be reached. We are either moving toward the destination of perfection, or we moving toward its opposite: “Just as the end of life is the beginning of death, so also stopping in the race of virtue marks the beginning of the race of evil” (I.6).
Gregory then introduces one of his most important contributions to Christian theology—the life of virtue knows no bounds because it is participation in the infinity of the divine nature:
The Divine One is himself the Good (in the primary and proper sense of the word), whose very nature is goodness. This he is and he is so named, and is known by this nature. Since, then, it has not been demonstrated that there is any limit to virtue except evil, and since the Divine does not admit of an opposite, we hold the divine nature to be unlimited and infinite. Certainly whoever pursues true virtue participates in nothing other than God, because he is himself absolute virtue. Since, then, those who know what is good by nature desire participation in it, and since this good has no limit, the participant’s desire itself necessarily has no stopping place but stretches out with the limitless.
It is therefore undoubtedly impossible to attain perfection, since, as I have said, perfection is not marked off by limits: The one limit of virtue is the absence of a limit. How then would one arrive at the sought-for boundary when he can find no boundary? (I.7-8)
That God is infinite being has long been commonplace to Christian theology and catechesis; but it was a revolutionary assertion in the fourth century. If the divine nature is infinite, then that necessarily entails that he is incomprehensible, for to know something is to be able to state a definition of what it is. As Albert-Kees Geljon writes: “In classical theology one of the attributes ascribed to God is infinity, for instance by Thomas Aquinas (Summa Theologiae 1 7 1) or Bonaventura (De mysterio trinitatis q.4 a.l conci.1). This is a startling contrast with the Greek philosophical tradition of Plato and Aristode, in which infinity—seen as undetermined and imperfect—is never predicated of the highest being (“Divine Infinity in Gregory of Nyssa and Philo of Alexandria,” Vigiliae Christianae 59 : 152). Even the great Origen, whose writings exercised such strong influence upon Gregory, has been commonly understood as resisting the notion of divine infinity: how could God comprehend himself if his nature were boundless and indeterminate? More recently, though, Panagiōtēs Tzamalikos has argued that Origen did attribute infinity to the divine essence:
The very use of the notion ‘infinite’ itself constitutes an outstanding point of contrast between Greek and Christian thought. Whereas the Greeks are very shy in attributing infinity to God, the Christians (on this following Philo) speak of God as infinite without any hesitation at all. In the Christian Fathers there is a close connection between the infinity and the incomprehensibility of God. My discussion here shows that Origen himself has no hesitation in attributing infinity to God in the most explicit terms. Thus he contributed to the establishment of what today is regarded as a major conceptual (as well as linguistic) contrast between Christians and Greeks. (Origen on Cosmology and Time, p. 247)
Tzamalikos comments that the popular thesis that Gregory was the first Christian theologian to think of God as infinite is unfair to Origen. In any case, Gregory was the first to develop in depth the infinitude of God and to make it decisive in his understanding of the spiritual life.
We can immediately see the importance of the divine infinitude for the Christian believer. If the spiritual life is nothing less than participation in God himself, then this life must be one of boundless progress. The translators of Vita Moysis, Abraham Malherbe and Everett Ferguson, elaborate:
Thus we come to the most distinctive teaching of the Life of Moses, and the theme that holds the whole work together, the idea of eternal progress. The ancients saw perfection in achievement, but Gregory (like the later Stoic moralists) denied the possibility of perfection in this sense. Developing hints in Philo and Origen, who had described the spiritual life as a succession of steps, Gregory went on to make progress itself perfection. Gregory Nazianzus expressed a similar idea of infinite progress in the never-completed journey to God. (p. 12)
Thus when Gregory speaks of virtue, he means something more profound than the mere achievement of moral excellence. I do not know yet if he uses the word theosis in this treatise, but it seems an apt term for the growth of virtue which he describes. We never reach a terminus in our deification in Christ. There is always more of God to know, more of God to contemplate, more of God to love, more of God to partake and enjoy.