I don't get it. The Lutherans, the Reformed, the Mennonites, the Evangelicals, the Methodists and thousand other protestant sects all differ among eachother. How can they all be led by the Holy Spirit? God is not the author of confusion.The idea that they are all different beliefs is a myth. Different denominations tend to emphasise different aspects of the truth. Their unity lies in their orthodox doctrine and the presence of the Holy Sprit in the church which flows from this. The critical issue is whether a church's doctrine is biblical and where this is the case I can happily worship in a Baptist, Methodist, Anglican, Pentecostal church.
How is the possibility of apostasy (Luther/Wesley/Methodists) a different aspect of your truth of the impossibility of apostasy and the necessity of certainty of future salvation? Would you allow that Methodists and Lutherans have "true faith" though they are not certain of future salvation, and if so how can you consistently deny that Orthodox do for the same reason? Is this a deal breaker for unity as you conceive of it or not?
How is baptismal regeneration (Luther, Calvin too though not later Calvinists) a different aspect of your truth that anyone affirming baptismal regeneration is therefore holding to a heretical idea of salvation by works (which Lutherans are not actually affirming, but denying, but you have claimed there is a necessary connection).
Many Pentecostals are Sabellian, that is to say they believe the Father, Son, and Holy Spirit are "modes" of one God and are not persons; they reject the doctrine of the Trinity. Do you regard these as in unity with what you consider the True Faith, and why or why not?
Other questions come to mind; I'll start with these. How much or how little can you dispense with and still have "unity without uniformity?" What for you is a "Non-Negotiable" and what isn't?
I get the impression that the Orthodox church does indeed claim infallibility even when its interpretations do not concur with scripture.
That is incorrect; Orthodoxy does not contradict scripture insofar as scripture is being interpreted correctly.
Therefore it sets itself above scripture..
This is also incorrect.
The age that something has been held to be true does not of itself make it true.
That is not false, but wouldn't you admit/allow it is at least far less suspicious if something was always affirmed from the very beginning? If say, Eternal Security as you affirm it were true, isn't it at least a little odd that ALL of the apostolic Fathers, like Polycarp the immediate disciple of John, like St. Clement who was bishop while the apostles were still alive, St. Ignatius who was bishop of Antioch (where Paul was) and all Syria during the lifetime of the apostles and who was ordained by the laying on of hands by the apostles, and the like believed in the possibility of apostasy? If "true apostolic doctrine" was the very opposite of that, wouldn't you expect there have been SOMEONE living at that time who would have presented at least one shred of dissent about a "key doctrine relating to salvation?" But the only ones that taught eternal security early on were heretics -the Gnostics taught that. So while that might be a hair short of what you who do not speak the language of the New Testament as your mother tongue like those folks did would consider proof, at the very least it seems to present not only more credibility to the ancient view, but also to put an incredible strain on the credibility of your position in that no church in any geographical region where the apostles directly appointed leaders taught what you teach, but rather they all taught the very opposite.
Neither does something become true just because an eminent person says it.
That is true; the word is understood correctly only by those who live it. St. Maximos the Confessor also emphasized this (see my post before last). But those who were ordained by the apostles, who laid their hands upon no man suddenly except they regarded them as "trustworthy men" have on the face of it at least a grain more of credibility than any group who teaches something opposite to what they did which is also completely unknown within all Christendom until many many centuries later. It is the latter sort of thing you seem to expect others to find credible, but why should they? Did the Holy Spirit exist within anyone who taught and wrote in those days in your view (if so please provide examples from very early centuries), or only in your day?
But because someone has believed something for 2000 years doesn't make it true.
Sure, but just because some fellow comes along well after 1800 years like Darby (the father of Dispensationalism) saying he has the Holy Spirit and has a doctrine opposite to everything known before doesn't make it true either, does it? Doesn't something taught for 2000 years and also by persons appointed by the apostles themselves or a direct disciple of an apostle seem a ***little*** more credible in your mind than a doctrine supposedly central to the Christian faith according to some later figure but taught by no one for many, many, many centuries?
I don't see how you have any assurance other than being very self confident if your own mind and then claiming it is the Holy Spirit.But either God meant it when he said he would send his Holy Spirit and that he would indwell all believers and lead them into all truth or God was lying. God tells us in his word what things we can be certain of, what things we can have assurance over. Do you personally know the indwelling of his Spirit?
But all Protestants acknowledge that heretics exist who affirm they have the Holy Spirit, but really don't. So subjective certainty that one has the Holy Spirit might be affirmed by someone who is actually a heretic, right? So how would a heretic or heterodox who believed he/she had the Holy Spirit know they did not? How do you/we know you are not heterodox or heretic?
As others have said your tenacity is admirable; I hope you feel you are welcome and in the presence of at least a few friends despite disagreements.