John Calvin on Those Who Refute the Authority of Scripture

"It is preposterous to attempt, by discussion, to rear up a full faith in Scripture.  True, were I called to contend with the craftiest despisers of God, I trust, though I am not possessed of the highest ability or eloquence, I should not find it difficult to stop their [boisterous] mouths; I could, without much ado, put down the boastings which they mutter in corners, were anything to be gained by refuting their [criticisms].  But although we may maintain the sacred word of God against gainsayers, it does not follow that we shall forthwith implant the certainty which faith requires in their hearts.  Profane men think that religion rests only on opinion, and therefore that they may not believe foolishly, or on slight grounds, desire and insist to have it proved by reason that Moses and the prophets were divinely inspired.  But I answer, that the testimony of the Spirit is superior to reason.  For as God alone can properly bear witness to his own words, so these words will not obtain full credit in the hearts of men, until they are sealed by the inward testimony of the Spirit.  The same Spirit, therefore, who spoke by the mouths of the prophets, must penetrate our hearts, in order to convince us that they faithfully delivered the message with which they were divinely entrusted.  This connection is most aptly expressed by Isaiah in these words, 'My Spirit that is upon thee, and my words which I have put in thy mouth, shall not depart out of they mouth, nor out of the mouth of thy seed, nor out of the mouth of thy seed's seed, saith the Lord, from henceforth and for ever' (Isa 59:21).  Some worthy persons feel disconcerted, because, while the wicked murmur with impunity at the Word of God, they have not a clear proof at hand to silence them, forgetting that the Spirit is called a [promise] and seal to confirm the faith of the godly, for this very reason, that until he enlightens their minds, they are tossed to and fro in a sea of doubts" (John Calvin, Institutes of the Christian Religion).