stylistic:tone, quality:correction
Universalism

Gregory was one of the earlier proponents of Christian universalism. Gregory argues that when Paul says that God will be "all in all" (1 Cor. 15:28), this means that though some may need to undergo a long period of purification, eventually "no being will remain outside the number of the saved" and that "no being created by God will fall outside the Kingdom of God". Due to the unity of human nature in Christ "all, thanks to the union with one another, will be joined in communion with the Good, in Jesus Christ Our Lord". Christ's incarnation, death and resurrection results in "total salvation for human nature".

Gregory also described God's work this way: "His end is one, and one only; it is this: when the complete whole of our race shall have been perfected from the first man to the last—some having at once in this life been cleansed from evil, others having afterwards in the necessary periods been healed by the Fire, others having in their life here been unconscious equally of good and of evil—to offer to every one of us participation in the blessings which are in Him, which, the Scripture tells us, 'eye hath not seen, nor ear heard,' nor thought ever reached." That this is what Gregory believed and taught is affirmed by most scholars. A minority of scholars have argued that Gregory only affirmed the universal resurrection.

In the Life of Moses, Gregory writes that just as the darkness left the Egyptians after three days, perhaps redemption will be extended to those suffering in hell. This salvation may not only extend to humans; following Origen, there are passages where he seems to suggest (albeit through the voice of Macrina) that even the demons will have a place in Christ's "world of goodness". Gregory's interpretations of 1 Corinthians 15:28 ("And when all things shall be subdued unto him...") and Philippians 2:10 ("That at the name of Jesus every knee should bow, of things in heaven, and things in earth, and things under the earth") support this understanding of his theology.

Nevertheless, in the Great Catechism, Gregory suggests that while every human will be resurrected, salvation will only be accorded to the baptised, although he also states that others driven by their passions can be saved after being purified by fire. While he believes that there will be no more evil in the hereafter, it is arguable that this does not preclude a belief that God might justly damn sinners for eternity. Thus, the main difference between Gregory's conception of ἀποκατάστασις and that of Origen would be that Gregory believes that mankind will be collectively returned to sinlessness, whereas Origen believes that personal salvation will be universal. This interpretation of Gregory has been criticized recently, however. After all, at the end of chapter XXXV of the Great Catechism Gregory writes that those who have not been purified by water through baptism "must needs be purified by fire" so that "after long succeeding ages, their nature may be restored pure again to God".

Attempting to reconcile these disparate positions, Eastern Orthodox theologian Dr. Mario Baghos notes that "when taken at face value the saint seems to be contradicting himself in these passages; on the one hand he asserted the salvation of all and the complete eradication of evil, and, on the other, that the fire needed to purge evil is 'sleepless', i.e. everlasting. The only solution to this inconsistency is to view any allusion to universal salvation in St Gregory as an expression of God's intention for humanity, which is in fact attested to when his holy sister states that God has "one goal... some straightway even in this life purified from evil, others healed hereafter through fire for the appropriate length of time." That we can choose either to accept or ignore this purification is confirmed by the saint's many exhortations that we freely undertake the virtuous path." Dr. Ilaria Ramelli has made the observation that for Gregory free will was compatible with universal salvation, since every person would eventually accept the good having gone through purification. Nevertheless, some interpret Gregory as conceding that Judas and similar sinners will never be completely purified when he wrote, "that which never existed is to be preferred to that which has existed in such sin. For, as to the latter, on account of the depth of the ingrained evil, the chastisement in the way of purgation will be extended into infinity". However, Ramelli renders the original Greek "εἰς ἄπειρον παρατείνεται ἡ διὰ τῆς καθάρσεως κόλασις" as "the punishment provided for the purpose of purification will tend to an indefinite duration." Additional sources are needed to interpret correctly the questioned chapter.