Proof texting is completely ineffectual as an apologetic tactic, because it marks a lack of understanding of the position of the opponent. For example, what purpose does it serve to present proof texts concerning Peter’s primacy to Orthodox Christians, who do not deny that Peter possessed a primacy among the apostles? Similarly what purpose does it serve to illustrate to Orthodox Christians that Rome was afforded a primacy of sorts in the first millennium, when nobody denies this? The difference is that the primacy of Rome, according to the Orthodox was neither inalienable, nor did it guarantee indefectibility to the Church of Rome. Similarly, while we understand the historical primacy of Rome to be based on the primacy of Peter, we understand in accordance with the great Eastern exegetes like the Cappadocians, St. John Chrysostom, St. Cyril and even some Western exegetes like St. Augustine, and St. Leo of most-blessed memory that the power and type of Peter is proposed to all pastors of the Church. That is to say, primates are primates in virtue of having received the power of Peter, possessed by all bishops, in their ordination.
This then renders about half of those texts (the ones taking about Peter’s primacy) meaningless in the context of discussion with the Orthodox, because we don’t even deny the primacy of Peter. Now for the Epistle of Clement, neither does this pose a problem for Orthodox Christians, because Rome had a long standing canonical right to appellate jurisdiction. It is also interesting to note that not once does the author of the Epistle of Clement mention the scriptural Petrine texts which would become the center point of the papacy’s claim to monarchal power during the Gregorian Reforms. Similarly one must recognize the ambiguity of that passage from the Latin translation of Irenaeus’ Against Heresies. By convenire does the translator mean agree or have recourse? The Latter is consistent with the canonical tradition, while the former interpretation seems not to have any support in the canonical tradition of the first millennium. The letter of St. Ignatius to the Romans is far too vague to support the modern Roman Catholic interpretation of primacy in favor of the Orthodox interpretation of the Roman primacy, as teaching and instructing are functions of all bishops, and not just of the bishop of Rome
As for Ss. Cyprian and Optatus, they must be interpreted in continuity with the whole of the Carthaginian tradition, namely St. Cyprian’s understanding that there is one Peter and one Episcopate in which all bishops are participants. Rome acts as a unifying beacon, but not as the sole possessor of the Episcopacy and Petrine ministry. This is how St. Cyprian could write glowing words of praise for the see of Rome on one hand, and take a defiant stand against St. Stephen on the other. St. Optatus similarly must be interpreted in the context of his debate with the Donatists. The Donatists argued that the marks of the Church were six (in contrast to Catholic Christians, who argue and continue to believe that the marks of the Church are four, that she is One, Holy, Catholic, and Apostolic). St. Optatus (perhaps by way of concession) grants them five of their six marks, and proceeds to show that the Catholic Christians possess all of them, while the Donatists possess none. One of these marks is the Cathedra (chair), and this, St. Optatus argues that the Catholic Church possesses, because the Donatists began their sect by schism, by trying to establish a second Cathedra. This passage is of limited apologetic value for two reasons. Firstly, it has never been a belief of Catholic Christians that ‘Cathedra’ is a mark of the Church, so to compare the East-West schism to the situation described by St. Optatus with the Donatists would be inadmissible. Secondly, even if we were to grant, against the perfect and unblemished faith expressed in the Niceno-Constantinopolitan Creed, that there existed a fifth mark of the church, Cathedra, St. Optatus clearly does not mean to say that the Cathedra is immutably attached to the city of Rome, but only that this city is where Peter first obtained the Cathedra, and through him, the entire Church gained this mark (though again, it must be stressed that this has never been a belief of Catholic Christians that Cathedra is a mark of the Church).