But the question is, are we capable of knowing either of these things?
Rome has thought we can since the third century. I don’t see why not.
Apophaticism concerning God is admirable. Apophaticism concerning whether our brothers and sisters in Christ are really our brothers and sisters in Christ is a bit more dubious.
Is it not better to confess our ignorance than to presume to know that which we know not?
Petitio principii. If this is really unknowable, sure. But the sacraments are given us at least in part, surely, in order to establish a visible community on earth. (Not denying that their purpose is theosis, only suggesting that we need physical means of theosis in part because purely spiritual means would result in an individualistic religion.) Knowing where that community is to be found is important. I don’t think absolute certainty is necessary, just a consistent means of discernment. (The Vatican has at one time been a lot more dubious about the validity of Protestant baptisms than it is today, and they went back and forth for a while about Mormons before deciding that their baptisms were invalid.)
But can the RCC justify its claim to know what we say we cannot know based on the Scriptures and Traditions?
By the guidance of the Holy Spirit, yes. And coming from a Protestant background, I’d justify the RC position based on Jesus’ words that where two or three are gathered in His name, He is there in the midst of them. The strict Cyprianic position seems to deny this. I simply don’t see that the Orthodox do justice to this and other passages in the NT (especially the Gospels) which point toward a far more generous understanding of the limits of the Church than St. Cyprian allowed for. The RCC has combined St. Cyprian’s doctrine of extra ecclesiam nulla salus (rooted in the clear Scriptural command of unity) with the Scriptural passages that point toward a more generous view.
But why is it a bad thing to make Florovsky’s admission?
Actually I don’t think it is. I’d be willing to make that admission about, say, Mormons.

But that’s because one can make a serious case that Mormons are in the fullest sense of the word outside the Church. As someone who has spent my entire life being spiritually nourished by forms of Christianity that are neither RC nor Orthodox (though I’ve certainly received about as much from those two Communions as it’s possible to do without belonging to either of them!), I have no doubt that Protestantism is in some sense within the Church. To doubt this would be to have little reason to go on being a Christian at all. The RC account explains my experience. The Orthodox account doesn’t even try to–it treats it as not even worth the effort. The RC account leaves room for the need to learn from non-Catholics. There’s little room in Orthodoxy for the need to learn from non-Orthodox. That may seem like a strength to you. It’s not a position I think I could ever accept (though the paradox is that I could accept it more readily of Orthodoxy than of anything else, which is one of the reasons I find choosing between the RCC and the EOC so hard!).
Can we presume to know the status of those outside of the confines of the Catholic Church? You see oikonomia as some sort of inconsistecy, while we see oikonomia as an admission that we know not, so the decision of how converts should be received is for the bishop to make, one which he will render account for on the day of judgment
I’d like to remind you that jam is the one who said that
Rome’s position was “schizophrenic.” My point is that this is an odd criticism for an Orthodox person to make.
I was not actually criticizing the Orthodox position in itself. I do find it frustrating for personal reasons, and that inclined me to think that maybe I’ve been too hard on Roman “juridicalism” at times. (I’ve never quite recovered from seeing a statement on an Orthodox forum to the effect that Rome recognizes sacraments outside its borders because of its “juridical” approach, while Orthodoxy, not being juridical, can’t do so. To my mind the advantage of not being “juridical” is that it leaves greater room for charity, but on this issue many Orthodox seem to take it in quite the opposite direction, which ruins any persuasive power their criticism of Rome’s “juridicalism” might have!) But in general I don’t find Roman criticisms of Orthodox “inconsistency” very compelling.
Now as for the Old Calendarists, I don’t see how they show that Orthodoxy is inconsistent any more than the sedevacantists show Catholicism to be inconsistent.
I’ve argued that case myself

. But I think there is a difference. I’m not talking about the Old Calendarist position per se but the broader “anti-ecumenical” position. Generally that tends to line up with Old Calendarism for obvious reasons.
Am I wrong that monasticism is the spiritual heart of Orthodoxy, credited with often maintaining the Faith when the hierarchy has failed?
Am I wrong that Mount Athos is one of the most important centers of Orthodox monasticism?
Am I wrong that many monks of Mount Athos consider Patriarch Bartholomew a heretic?
If I’m not wrong about these things, then this is very different from the truly marginal phenomenon of Catholic sedevacantism.
But is it necessary to have uniformity? What if they are wrong? We’re not playing with intellectual issues here, human salvation is on the line.
I’m a bit baffled by this argument. If human salvation is on the line, surely uniformity is a good thing? If Bishop X is erring in admitting people without baptizing them, and thus putting his and their salvation on the line, wouldn’t it actually be a good thing to have something like the Vatican’s ability to tell Bishop X “no”?
If one bishop admits me to Orthodoxy without baptizing me, and takes the responsibility of answering for this at the Judgment, and I then move to the jurisdiction of another bishop, wouldn’t that bishop need to rethink the whole thing or else answer at the Judgment for
his laxity? Doesn’t this start to unravel the whole conception of a visible Church?
I feel weird making this argument, because generally on this forum I argue the merits of the Orthodox approach, and in fact I only got into this because of what I found a weird argument from jam that
Rome was inconsistent. But I do find Rome’s approach preferable on this particular point. I think that “legalism” has its uses when it serves charity.
Edwin