Calvin writes in chapter 7 of his 'Institutes of the Christian Religion:'
... But he [Augustine] nowhere insinuates that the authority which we give to the Scriptures depends on the definitions or devices of men. He only brings forward the universal Judgment of the Church, as a point most pertinent to the cause, and one, moreover, in which he had the advantage of his opponents.
In context, he is essentially explaining away Augustine's statement against Manichaeus that, "For my part, I should not believe the gospel except as moved by the authority of the Catholic Church" (Against the Fundamental Epistle of Manichaeus, 5). Manichaeus simply asserted his authority in his Epistles. St. Augustine rejects this and cites the authority and testimony of the Church as a reason to believe the Gospel, contrary to the irrationality of simply believing on someone's word.
Again, if you say, You were right in believing the Catholics when they praised the gospel, but wrong in believing their vituperation of Manichæus: do you think me such a fool as to believe or not to believe as you like or dislike, without any reason? It is therefore fairer and safer by far for me, having in one instance put faith in the Catholics, not to go over to you, till, instead of bidding me believe, you make me understand something in the clearest and most open manner. To convince me, then, you must put aside the gospel. If you keep to the gospel, I will keep to those who commanded me to believe the gospel; and, in obedience to them, I will not believe you at all. But if haply you should succeed in finding in the gospel an incontrovertible testimony to the apostleship of Manichæus, you will weaken my regard for the authority of the Catholics who bid me not to believe you; and the effect of that will be, that I shall no longer be able to believe the gospel either, for it was through the Catholics that I got my faith in it; and so, whatever you bring from the gospel will no longer have any weight with me. Wherefore, if no clear proof of the apostleship of Manichæus is found in the gospel, I will believe the Catholics rather than you. But if you read thence some passage clearly in favor of Manichæus, I will believe neither them nor you: not them, for they lied to me about you; nor you, for you quote to me that Scripture which I had believed on the authority of those liars. But far be it that I should not believe the gospel; for believing it, I find no way of believing you too. For the names of the apostles, as there recorded, do not include the name of Manichæus. And who the successor of Christ's betrayer was we read in the Acts of the Apostles; which book I must needs believe if I believe the gospel, since both writings alike Catholic authority commends to me.
But Calvin says something which seems to evidence a vestigal appeal to the authority and consensus of the Church, something dropped (of necessity) as an epistemological test of orthodoxy during the Reformation. He says Augustine "brings forward the universal Judgment of the Church," in his argument against Manichaeus, as if something which would prove him the orthodox of the two. Indeed, were this a standard of who was right, Calvinism itself would not stand the test of the perennial judgement of the Church throughout the centuries, or in any particular one. And again he says, "a point most pertinent to the cause, and one, moreover, in which he had the advantage of his opponents."
According to Calvin, why is "the universal judgement of the Church" "pertinent" in a dispute with a heretic, if Calvinism itself would not, by anyone's account, withstand this criteria? How does it give Augustine the "advantage?"