I think you probably have to look at it collectively rather than individually - which should not be a surprise as Christianity is a collectivist religion in many ways.
The idea being, I think, that in Orthodoxy the heretical views of that individual are not going to be able to infect the whole of the Church in any meaningful way. If they are expressed, the OC deals with them, possibly to the point where the heretical individual or group becomes excluded from the institutional Church. Because they see that this has always worked for them in the past (over the long term anyway) they are confident in their own apostolic succession and access to sacraments as a Church.
(Of course if we could show this is historically not the case, this argument would be untenable.)
But MKJ, either your parish priest is a
real priest, or he's not. And when he communes you, either what he gives you is really and truly the Body and Blood of Christ, or it's still the ordinary bread and wine that was originally offered. Whether or not your priest, as an
individual person, has received a valid ordination makes
all the difference between his having the authority to celebrate the Eucharist, absolve sins, etc. and his being an ordinary layman with no authority to do such things at all.
Yes, Christianity is a collectivist religion in some ways; in other ways, however, it is rather rigidly individualistic. Take baptism, for example. My baptism is my own individual baptism. It doesn't count as your baptism (or anyone else's, for that matter). You have to receive your own individual baptism. Also, an act of baptism must meet certain criteria if it's to be valid. A priest can't tap a person on the head three times with a Bible while reciting the baptismal formula and have that count as a valid baptism. No, he has to use water, and he has to use it in a washing capacity (he can't have you drink it, say). And further, neither he nor anyone else can re-baptize you. Baptism is an
indelible sacrament, meaning that once the sacrament has been validly performed for an individual person, it
cannot be repeated for that individual person. To intentionally repeat an indelible sacrament for the same person is sacrilege. This is why care must be taken to determine whether or not an individual has received a valid baptism, and that individual must
not be baptized unless it can be determined with reasonable certainty that that he or she has not already been validly baptized.
All of this also applies to holy orders. Holy orders are individualistic. An individual person is individually ordained, just as he is individually baptized. Also, in order for a person's orders to be valid, certain validating criteria must be met. In post #46 I provided a list of four criteria which both Romans and Anglicans accept, where the sufficient conditions for the first criterion are a simple repetition of those four for the performing minister (and so on, going all the way back to the Apostles). And further, just as with baptism, holy orders are indelible. It is
not lawful to ordain a man (to
unconditionally ordain him, at the very least) unless it can be determined with reasonable certainty that he has not already been ordained.
This is why it seems necessary to me that we have well-defined criteria for the validity of holy orders on the table for careful analysis and critical scrutiny if ecumenical dialogue is to move forward. We need to have such criteria in order to determine who,
individually, is a deacon, presbyter, or bishop. Otherwise, I don't see how we could determine whether a given celebrant is celebrating a valid Eucharist, etc.
On the other hand, this has evidently not been the case in Anglicanism, and it is debatable whether we even say that it should be true theoretically. Heretical bishops have been allowed to infect Anglican doctrine. We now have people who think they can have a blessed sexual relationship that is not a marriage, that the laity can confect the Eucharist, that the Eucharist can be given to dogs, that apostolic succession is unimportant. These are acceptable views at Anglican theological colleges. When I look at the various traditional Anglican groups, one of my first thoughts is that there is really nothing preventing the same thing happening in them. When someone like Spong can be allowed not only to lead, but teach perfidious doctrine, how could we know that he is not so far away from Christian teaching that he can even function as a bishop.
But yet, the fact remains that there
are orthodox Anglicans who will have no part in such abominations. Orthodox Anglicanism has
not been entirely stamped out, and I can see no reason to think that it will ever be. Perhaps heresies and schisms will eventually come to plague the traditional groups, but has Orthodoxy been entirely free of having to deal with these?
That is the real issue with the way Westerners talk about validity - while holding a heretical view does not in itself invalidate an office, at some point it begins to impact things like intent. Can someone who believes that Christianity is a sort of metaphor have intent, for example. And Spong is not alone - I know of other bishops with similar views that are not well known. Do those bishops really connect us to the Church,. And what about the priests they ordain.
As far as intent goes, all the minister has to do is intend to do what the Church intends by the sacrament. That's it. He might be an atheist and think it's all a just bunch of hocus pocus nonsense, but as long as he intends to perform what the Church understands to be, e.g., an act of holy baptism, then he performs a valid baptism, provided he does it according to acceptable form (i.e. that he recites the proper baptismal formula) and matter (i.e. that he employs the proper use of water) of course.
Who knows, really. After a generation, maybe a declaration of belief would suffice to weed out those returning. After 10 generations, well, it is hard to say if apostolic secession is intact or not, especially for someone who is not actually a member of the group.
It seems to me that the Orthodox Church should have well-defined and rigorously-defensible criteria in place in order to settle such matters. Any good Anglican cleric who's told that he'll have to be unconditionally reordained is going to ask why, and he's going to require an acceptable and rigorously-defensible answer. This is not a matter of pride. It's a matter of unlawfully and sacrilegiously repeating an indelible sacrament.