We ought to remember what I said a bit ago: credibility of doctrine is not established until we are persuaded beyond doubt that God is its Author. Thus, the highest proof of Scripture derives in general from the fact that God in person speaks in it. The prophets and apostles do not boast either of their keenness or of anything that obtains credit for them as they speak; nor do they dwell upon rational proofs. Rather, they bring forward God’s holy name, that by it the whole world may be brought into obedience to him. Now we ought to see how apparent it is not only by plausible opinion but by clear truth that they do not call upon God’s name heedlessly or falsely. If we desire to provide in the best way for our consciences — that they may not be perpetually beset by the instability of doubt or vacillation, and that they may not also boggle at the smallest quibbles — we ought to seek our conviction in a higher place than human reasons, judgments, or conjectures, that is, in the secret testimony of the Spirit. True, if we wished to proceed by arguments, we might advance many things that would easily prove — if there is any god in heaven — that the law, the prophets, and the gospel come from him. Indeed, ever so learned men, endowed with the highest judgment, rise up in opposition and bring to bear and display all their mental powers in this debate. Yet, unless they become hardened to the point of hopeless impudence, this confession will be wrested from them: that they see manifest signs of God speaking in Scripture. From this it is clear that the teaching of Scripture is from heaven. And a little later we shall see that all the books of Sacred Scripture far surpass all other writings. Yes, if we turn pure eyes and upright senses toward it, the majesty of God will immediately come to view, subdue our bold rejection, and compel us to obey. Yet they who strive to build up firm faith in Scripture through disputation are doing things backwards. For my part, although I do not excel either in great dexterity or eloquence, if I were struggling against the most crafty sort of despisers of God, who seek to appear shrewd and witty in disparaging Scripture, I am confident it would not be difficult for me to silence their clamorous voices. And if it were a useful labor to refute their cavils, I would with no great trouble shatter the boasts they mutter in their lurking places. But even if anyone clears God’s Sacred Word from man’s evil speaking, he will not at once imprint upon their hearts that certainty which piety requires. Since for unbelieving men religion seems to stand by opinion alone, they, in order not to believe anything foolishly or lightly, both wish and demand rational proof that Moses and the prophets spoke divinely. But I reply: the testimony of the Spirit is more excellent than all reason. For as God alone is a fit witness of himself in his Word, so also the Word will not find acceptance in men’s hearts before it is sealed by the inward testimony of the Spirit. The same Spirit, therefore, who has spoken through the mouths of the prophets must penetrate into our hearts to persuade us that they faithfully proclaimed what had been divinely commanded. Isaiah very aptly expresses this connection in these words: “My Spirit which is in you, and the words that I have put in your mouth, and the mouths of your offspring, shall never fail” Isaiah 59:21 p.]. Some good folk are annoyed that a clear proof is not ready at hand when the impious, unpunished, murmur against God’s Word. As if the Spirit were not called both “seal” and “guarantee” 2 Corinthians 1:22] for confirming the faith of the godly; because until he illumines their minds, they ever waver among many doubts!
Let this point therefore stand: that those whom the Holy Spirit has inwardly taught truly rest upon Scripture, and that Scripture indeed is self-authenticated; hence, it is not right to subject it to proof and reasoning. And the certainty it deserves with us, it attains by the testimony of the Spirit. For even if it wins reverence for itself by its own majesty, it seriously affects us only when it is sealed upon our hearts through the Spirit. Therefore, illumined by his power, we believe neither by our own nor by anyone else’s judgment that Scripture is from God; but above human judgment we affirm with utter certainty (just as if we were gazing upon the majesty of God himself) that it has flowed to us from the very mouth of God by the ministry of men.