I take the premise of the parable metaphorically: landlord is Christ and the Kingdom of Heaven is a lending institution. This is by necessity, because it is a parable we are dealing with. But I refuse to ignore elements of the parable because if they are mentioned, they are of essence for our understanding. Regarding this question of yours, we are to presume that the proceeds fo the sale into slavery satisfied the debt. There is nothing however in the original judgement that suggests that the slavery was temporary: "his lord commanded that he should be sold, and his wife and children and all that he had, and payment to be made".
a failure to forgive others is considered to be the single most spiritually dangerous thing that a person can do
Yes, it is a difficulty, because we are certainly commanded to do works of charity and mercy, and the debtor failed at that. I would take into account two factors: (1) the debtor was passionate about the debt owed him (v. 28); (2) the debtor volunteered to pay off the ten thousand talent debt (v.26). It is then reasonable to conclude that the failure to forgive the small debt was a venial sin of passion, -- the debtor was driven by the reasonable to him desire to collect what was rightly his and repay the landlord. This is, of course, the secondary meaning of the parable: that the economic view of sin as debt, under which the debtor invincibly operates, is really supplanted by the law od charity and mercy.
your reading was likewise heavily influenced by the specifics of the Catholic spiritual/confessional life
That could be, but if you carry out of this the impression that a failure of charity is generally treated lightly in Catholicism, that would be a wrong conclusion.
it is *precisely* what St. Gregory of Nyssa is saying, so I'm not sure how you can take him as support.
In the passge cited, he simply states
"...the indebted man was delivered to the tormentors until he should pay the whole debt; and that means nothing else than paying in the coin of torment the inevitable recompense, the recompense, I mean, that consists in taking the share of pain incurred during his lifetime, when he inconsiderately chose mere pleasure, undiluted with its opposite; so that having put off from him all that foreign growth which sin is, and discarded the shame of any debts, he might stand in liberty and fearlessness
This passage is a beautifully stated Catholic concept of redemptive suffering, contains no speculation about forgiveness of every sinner, and describes the conclusion of the parable with precision.
"This passage is a beautifully stated Catholic concept of redemptive suffering, contains no speculation about forgiveness of every sinner, and describes the conclusion of the parable with precision."
But you only quoted the first portion of what I gave from St. Gregory (which I did in the interest of fairness, since it was the only quotation from an Eastern Father that I could find that could possibly be used to support your reading of that passage in St. Matthew.) He does not give an exegesis of the passage, but just makes a passing reference to that one line, BTW.
The concluding section of that same passage, that I also quoted, was this:
"But He that becomes "all" things will be "in all" things too; and herein it appears to me that Scripture teaches the complete annihilation of evil.
If, that is, God will be "in all" existing things, evil, plainly, will not then be amongst them;
for if any one was to assume that it did exist then, how will the belief that God will be "in all" be kept intact?
The excepting of that one thing, evil, mars the comprehensiveness of the term "all."
But He that will be "in all" will never be in that which does not exist." "
In other words, St. Gregory is using the "until all the debt should be paid" quotation in the context of his argument that someday evil will be, must be, completely annihilated, and by extension (putting this together with more explicit passages) that all will be saved because everyone will eventually pay their debt in hell -- and because God cannot be "in all" as long as any evil exists. He is not talking about the purification of the saved, but the ultimate redemption of the damned.
I am not saying that a lack of charity is treated lightly in Catholicism. I'm not sure that I could at all describe the man's actions as being a mere "lack of charity." A failure to love one's neighbor is a serious failing -- but refusing to forgive someone who begs for forgiveness goes beyond that to something far more basic -- for we can choose actively to forgive even those towards whom we have no love. It is more akin to direct hatred, and the debtor's actions are, as the several Eastern Fathers describe it, "savage" -- he seizes the man begging for forgiveness by the throat, as though he were an animal. This is a depiction of a "venial sin?" Maybe I don't understand the subtleties of what makes something a venial sin.
"This is, of course, the secondary meaning of the parable: that the economic view of sin as debt, under which the debtor invincibly operates, is really supplanted by the law of charity and mercy."
Of course it is so supplanted. But yet you find in this story support for the essentially economic view of purgatory (a combination of unforgiven venial sins and uncompleted penances are quantified by God and must be paid for and cleansed by a certain amount of time in the fires of purgatory -- a man with a single unforgiven venial sin and no uncompleted penances will spend much less time in purgatory than will a man with a host of unforgiven venial sins and a lot of uncompleted penances.)
In the end, since you do not claim that this passage is one cited by Catholic authorities as support for purgatory, but is rather your own personal reading, I don't want to be guilty of beating this horse endlessly, and will try to leave my comments at this. In my own defense, my original response was (unusually, for me) a mere one-liner!