John Calvin on the Holy Spirit and the Credibility of Scripture

"With what confidence it becomes us to subscribe to a doctrine attested and confirmed by the blood of so many saints?  They, when once they had embraced it, hesitated not boldly and [courageously], and even with great [eagerness], to meet death in its defense.  Being transmitted to us with such an earnest, who of us shall not receive it with firm and unshaken conviction?  It is therefore no small proof of the authority of Scripture, that it was sealed with the blood of so many witnesses, especially when it is considered that in bearing testimony to the faith, they met death not with fanatical enthusiasm (as erring spirits are sometimes wont to do), but with a firm and constant, yet sober godly zeal.  There are other reasons, neither few nor feeble, by which the dignity and majesty of the Scriptures may be not only proved to the pious, but also completely vindicated against the [complaints] of slanderers.  These, however, cannot themselves produce a firm faith in Scripture until our heavenly Father manifest his presence in it, and thereby secure implicit reverence for it.  Then only, therefore, does Scripture suffice to give a saving knowledge of God when its certainty is founded on the inward persuasion of the Holy Spirit.  Still the human testimonies which go to confirm it will not be without effect, if they are used in subordination to that chief and highest proof, as secondary helps to our weakness.  But it is foolish to attempt to prove to infidels that the Scripture is the word of God.  This it cannot be known to be, except by faith.  Justly, therefore, does Augustine remind us, that every man who would have any understanding in such high matters must previously possess piety and mental peace" (John Calvin, Institutes of the Christian Religion).