Reading Plato Toward the Christian God

Gregory of Nyssa's theology drew more openly on Platonist philosophy than either his brother's or Gregory of Nazianzus's, and he used it to defend the same Nicene position, that Father, Son and Holy Spirit share one divine nature while remaining three distinct persons, through arguments about universal and particular natures borrowed from Greek philosophical logic. His treatise Against Eunomius is among the most technical philosophical defenses of Nicene Trinitarianism to survive from the period, answering a radical Arian theologian who had argued that the very meaning of the word unbegotten proved the Son could not be fully divine.

Gregory is remembered today at least as much for a different kind of writing, his Life of Moses, which reads the biblical account of Moses ascending Sinai into darkness to meet God as an allegory for the soul's endless approach toward an infinite God who can never be fully comprehended, a state Gregory called epektasis, perpetual reaching forward, arguing that even in the next life the soul does not arrive at a final rest but keeps moving deeper into God without end. This idea, and his related teaching that evil has no independent existence but is only the absence or privation of good, influenced later Christian mysticism, particularly in the Eastern tradition, far beyond the immediate theological disputes of his own century. He died around 395, some years after both his brother and his friend Gregory of Nazianzus.