The patristic Protestant scholar Theodore Zahn's article on the regula fidei which is found at Calvin's College Christian Classic's database (which can be found here ) is superb in it's objectivity.
"Different forms with more or less the same meaning occur. Ho kanon tes aletheias ("canon of truth "), regula veratatis (rule of truth), probably the oldest form, was used apparently by Dionysius of Corinth (c. 160), then by Irenseus, Clement of Alexandria, Hippolytus, Tertullian, and Novatian; ho kanon tes pisteos, regula fidei, by Polyerates of Ephesus, Clement of Alexandria, Tertullian, and by the later Latin writers. The equivalent use of these two expressions is important for the determination of the original significance attached to them. The truth itself is the standard by which teaching and practise are to be judged (cf. Ireneeus, H�r, II., xxviii. 1; ANP, i. 399). It is presupposed that this truth takes for the Christian community a definite, tangible form, such as the law was for the Jews (Rom. ii. 20), in a body of doctrine not merely held and taught by the Church, but clearly formulated." [Emphasis mine].
Thus we see that the regula fidei early on was a set of theological propositions that were universally held and defended. By definition this implies unanymity. For it can hardly be conceived that the early orthodox Church would have clung to an eclectic and multivarious set of doctrines. What Zahn fails to mention, is that the reason the early Catholic communities held so steadfastly to this faith was their perceived understanding that this faith was the same as that held by the Apostles themselves and was hence handed down.
"The ante-Nicene church never considered as the Rule of Faith the Bible or any part of it. Certain expressions of recent writers show that it is not unnecessary to point out that the word kanon, with or without qualifying additions, is never used until after Eusebius to designate the Bible, and that even after the word had begun to be applied to the collection of Scriptural books, the sense mentioned 446 above is never given to it by the Greeks. This is explained by the fact that the early Church used this word for something else-the baptismal formula." [Emphasis mine].
A telling admission from one of Protestantism's greatest patristic scholars. There is no need to bend the evidence (as is so frequently done today). The patristic testimony is clear and unambiguous. The idea of "sola Scriptura" as the sole rule for the faith of the earliest Christian Churches is simply lacking in the historical accounts. Instead, it is the entire body of the faith that was held as the source or rule or gauge - that was the norm of authority for Christians,
"In a word, the early Fathers considered Christ himself as the giver of the Rule, though they admitted freely that its actual words were an expansion of the nucleus recorded in the Gospels, regarding it as only a development of the baptismal formula; and, on the other hand, the whole body of teaching current in the undisputed Catholic Church was to them but an expansion of the creed, and thus the term " Rule of Faith " could be, as it is occasionally found, applied to this whole body."