In effect, the Reformation sought to purge the church from its later, unbiblical accretions.
In the sense that the Protestant churches are Biblical, that is where they achieve their "validity"
authority is simply a lie that has been foisted on Christianity, and
it's something that the mindless and the thoughtless and the deceived
have latched onto.
it may have been descriptive of the way that the second century
church established its legitimacy vis-a-vis the Gnostics, but to then
turn that around and suggest that this method "is prescriptive for all
time" is a heinous usurpation of Christ's own authority in the church.
You must all follow the lead of the bishop, as Jesus Christ followed that of the Father; follow the presbytery as you would the Apostles; reverence the deacons as you would God's commandment. Let no one do anything touching the Church, apart from the bishop. Let that celebration of the Eucharist be considered valid which is held under the bishop or anyone to whom he has committed it. Where the bishop appears, there let the people be, just as where Jesus Christ is, there is the Catholic Church. It is not permitted without authorization from the bishop either to baptize or to hold an agape; but whatever he approves is also pleasing to God. Thus everything you do will be proof against danger and valid.  (emphasis added)
St. Irenaeus "The blessed apostles [Peter and Paul], having founded and built up the church [of Rome] . . . handed over the office of the episcopate to Linus" (Against Heresies 3:3:3 [A.D. 189]). 
Cyprian of Carthage
"The Lord says to Peter: ‘I say to you,’ he says, ‘that you are Peter, and upon this rock I will build my Church, and the gates of hell will not overcome it. . . . ’ [Matt. 16:18]. On him [Peter] he builds the Church, and to him he gives the command to feed the sheep [John 21:17], and although he assigns a like power to all the apostles, yet he founded a single chair [cathedra], and he established by his own authority a source and an intrinsic reason for that unity. . . . If someone [today] does not hold fast to this unity of Peter, can he imagine that he still holds the faith? If he [should] desert the chair of Peter upon whom the Church was built, can he still be confident that he is in the Church?" (The Unity of the Catholic Church 4; first edition [A.D. 251]). 
Eusebius of Caesarea
"Paul testifies that Crescens was sent to Gaul [2 Tim. 4:10], but Linus, whom he mentions in the Second Epistle to Timothy [2 Tim. 4:21] as his companion at Rome, was Peter’s successor in the episcopate of the church there, as has already been shown. Clement also, who was appointed third bishop of the church at Rome, was, as Paul testifies, his co-laborer and fellow-soldier [Phil. 4:3]" (Church History 3:4:9–10 [A.D. 312]). 
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