A passage in Gregory of Nyssa' Great Catechism struck me:
"Now, to the pure, freedom from passion is that kindred state, and that in this freedom from passion blessedness consists, admits of no dispute. But as for those whose weaknesses have become inveterate, and to whom no purgation of their defilement has been applied, no mystic water, no invocation of the Divine power, no amendment by repentance, it is absolutely necessary that they should come to be in something proper to their case,—just as the furnace is the proper thing for gold alloyed with dross,—in order that, the vice which has been mixed up in them being melted away after long succeeding ages, their nature may be restored pure again to God. Since, then, there is a cleansing virtue in fire and water, they who by the mystic water have washed away the defilement of their sin have no further need of the other form of purification, while they who have not been admitted to that form of purgation must needs be purified by fire." (chap. XXXV).
Does Gregory here seem to imply that those who have not been purified through baptism somehow must go to some sort of purgatory? This idea seems to be reinforced by the introductory sentence of the following chapter ("For common sense as well as the teaching of Scripture shows that it is impossible for one who has not thoroughly cleansed himself from all the stains arising from evil to be admitted amongst the heavenly company.") Yet I thought that the idea of such purification by fire never developped in the Orthodox world as it did in Catholicism.
I think it would be too crude to say that suddenly the East gathered all the wisdom without any problem at all, while the West was devoted to failure without any merit at all. Fathers of the East, even the greatest, such as Gregory of Nyssa, may have beliefs that are wrong. The Church in the Ecumenical Synods did not accept everything that great Fathers and theologians taught and (here is an immense difference with the West), she did not feel obliged even to condemn those Fathers for keeping some wrong ideas, i.e., the Church in the East recognised holiness and faith, at least to some degree, beyond beliefs.
However, note that even St Gregory of Nyssa never denied eternal hell. There is indeed some flirtation with the idea of a purgatory that would destroy all evil, but only that. Note, for example, this great remark of St Gregory in his speech on the infants, according to which hell and purgatorium are the same: "if the evil is born deep inside someone, through purgation the hell goes on and on forever..."
We must read a page in the context of the whole book and the book in the broader context of all the books of an author. This way we can see that, no matter how close Gregory came to the idea of a purgatorium, he rather believed that there is a katharsis, a purgation, that may extend forever without ever consuming all evil, which means that Gregory never stopped believing to the freedom of human will, and to the paradoxical ways this freedom may choose to follow.