excerpt from Select Works of Robert Rollock, vol. 1, pp. 68-73.
Scripture is autopistos (self-authenticating)
How and by what evidence this may appear, that the Scripture is God’s word? To this I answer on this manner: That we have no need simply of any other light, or of any one special evidence to demonstrate this matter, but that very light which is in the Scripture. For the Scripture (being the first and immediate word of God) is of authority sufficient in itself, and so likewise of itself most clear and evident, and the only cause of all that light which is in the Church and in the hearts of men. For like as the light of the sun is not perceived nor to be seen by means of any other light, for that it so far exceeds all other bodily and external light, so, that spiritual light of the Scripture hath no need in itself of any other light to set forth the same, for that of all spiritual lights to enlighten the mind withal, it is the most bright and most beautiful in the world.
But whereas evidences and demonstrations be here demanded for the proof of this matter, to confirm the Scripture to be God’s word, that is, to be the very light, the cause of this doubtfulness is in ourselves, for that we be so blear-eyed and so blind by nature. Wherefore, the arguments which are brought for this purpose add no light to the light of the Scripture, which is of its own nature so clear, and cannot be made to shine more bright by any addition, but all serve to this end, to make that thing manifest unto us which is most evident in itself, and that our eyes may be opened to see that most full and most glorious light of the sacred Scripture: that is, to behold the divine majesty of God shining bright, and speaking unto us in the holy Scripture. Like as if a man were to prove to a blind man that the sun did shine, he would not produce arguments to commend the excellency of the light of the sun, but rather provide such things as whereby, if it were possible, he might open the eyes of the blind, that with his own eyes he might look on the glorious light of the sun. Wherefore, in a word, whatsoever arguments men ask of us to demonstrate the light of the Scripture, they ought not to be demanded because of any defect in the Scripture, but in respect of us, because we be so blind, having need of all arguments and helps every way to open our eyes, that our sight may be quickened to behold this glorious light.
The Holy Ghost speaking in Scripture
The arguments and helps whereby our eyes may be opened to behold the light of the Scripture, or God speaking and shining in the Scripture — these arguments, I say, which the godly and learned use for this purpose, be not of one sort, but many in number. But if the Holy Ghost, speaking in the Scripture, do not first of all inspire our minds, and open the eyes of our understanding (Eph. 1:16-17), for he alone can do it, assuredly it is but lost labour to speak of any other argument or help; if we be not taught of God, and by his Holy Spirit, all other means shall profit us nothing at all. Wherefore, the first and most principal cause to effect this, that we may behold the light of the Scripture, so bright in itself, must be the Holy Ghost teaching us inwardly in our hearts, and opening our understanding, that we may behold that light of the Scripture, and may acknowledge the voice of God, and of Christ himself, speaking in the Scripture. And the Holy Ghost also himself in this work gives no new light to the Scripture, which is clear and glorious in itself, as is aforesaid, but enlightens our minds, to this end, that we may see the great light of the sacred Scripture. Again, the Holy Ghost, in this great work of our illumination, effects it by certain means and instruments, whereby it pleases him to work in our hearts and minds.
The means used by the Holy Spirit, Internal and External
The means which the Holy Ghost uses for this work are of two kinds. The first is internal; the second is external. The inward mean is in the very Scripture itself; the outward is without the Scripture. The internal mean is the principal organ or instrument of God’s Spirit in this work, and it is that very light which the shines in the Scripture. The Holy Ghost, then, doth first of all open the eyes of our understanding, by the light of the Scripture, to discern that light of the Scripture, so bright in itself, and so unknown unto us. And he clears our understanding, to see the light of the Scripture, by the very Scripture itself and by the light of the Scripture, many ways.
Inward means to see the light of the Scriptures
For partly he effects this by:
1) producing certain testimonies of Scripture which plainly testify great light of the Scripture, and of God speaking in the Scripture, as that place. “All Scripture is given by divine inspiration” (2 Tim. 3:16);
2) partly by suggesting into us, that we observe the spiritual matters which are therein described;
3) partly by admonishing that we note the spiritual words whereby the same spiritual matters are expressed and set before us;
4) partly by warning us to observe the truth of the divine oracles by the complement of the prophecies.
5) Again, he sets before us the beautiful harmony of the Scripture in the Old and New Testament, the one sweetly testifying of the other.
6) And here he omits not the miracles which he records therein, whereby the celestial doctrine had in the beginning a confirmation. He puts us also in mind of the martyrs which sealed the same truth with their blood, as we read in the same Scripture.
By these means, and such like, the Spirit teaches us out of the very Scripture, that the sacred Scripture is God’s word, by clear evidence manifesting that great and excellent light which is in the Scripture. Add also unto the aforesaid means, the worth and holiness of those men which wrote the Scriptures, as the same is testified and recorded in the Scriptures. And this is the internal and principal mean and instrument of the Holy Ghost, whereby he teaches us and breeds faith in our hearts, whereby we be certainly persuaded that this Scripture is the very word of God.
External means to prove the Scripture to be God’s Word
There are also other means without the Scripture, whereby the Spirit proves the same thing, as:
1) the constancy of the martyrs, which daily seal with their blood the truth of this heavenly doctrine;
2) the persecution raised by the enemies of the Church against it,
3) the enmity of Satan against it,
4) the preservation of the divine oracles of God unto our times;
5) and, to be short, the testimony of the true Church of God for it.
All these are without or beside the Scripture, and give us a secondary kind of demonstration, whereby the Holy Ghost works also, as it pleases him, and opens the eyes of our understanding, enlightening us to see and hear God himself speaking and shining in the Scripture.
God, by these means (the testimony of the Church and conversation of the saints) prepares us to receive the precious faith (John 4; 1 Peter 3:2-3)
But here we be to observe, that the Holy Ghost does not beget faith in our hearts, properly and principally, by this second kind of external means,—for the proper and principal instrument of God to breed faith is the very Word of God himself, for it must be, necessarily, either the lively voice of God or the sacred Scripture, which serves us instead of the lively voice of God himself,—but either prepares our hearts only to receive faith afterwards by the Word of God, or to confirm the same in some sort, being already engendered in our hearts by God’s word. For this cause, this second kind of means sometimes is sent before the voice of God in the Scripture, whereby the Holy Ghost otherwhiles makes men’s minds ready to entertain faith and grace offered. This we read of Augustine, for he speaks it of himself, “I would not have believed the gospel, hut that the authority of the Catholic Church moved me thereunto;” by which words he means, that when he was a Manichee, he was prepared by the authority and testimony of the Church to believe the gospel. Afterwards, not withstanding, the same Holy Spirit which thus prepared him by the testimony of the Church,—I say, the same Spirit did beget faith in Augustine’s heart by the very Scripture of the gospel, whereby he did believe that the gospel was the very word of God. For this cause he speaks elsewhere of himself. “And let us follow them (saith he) which do invite us first to believe that which we cannot behold as yet, that being strengthened by faith itself, we may be worthy to understand what we believe, not by the relation of men, but by the grace of God himself inwardly confirming and enlightening our minds.”
Win them with your conversation, which are without the word (1 Peter 3:1-2)
So the woman of Samaria, (John 4:39) as a member of the Church, did, by her kind of preaching, prepare the Samaritans to the faith of Christ, and they having heard Christ himself, said to the woman. “We believe no longer because of thy sayings, for we have heard him ourselves, and know that this is indeed the Christ, the Saviour of the world” (John 4:42). By which words they plainly testified, that they were prepared only by the woman’s testimony to embrace the faith, and that faith was engendered in their hearts by the powerful voice of Christ himself. Wherefore, it is clear that sometimes this kind of mean and argument, as is aforesaid, goes before faith, is begotten in the heart to prepare us. And sometimes this follows faith for confirmation. And sometimes, also, this kind of argument [both] goes before faith, and follows after it: it goes before, I say, for preparation; it follows after for confirmation. For the Spirit teaches us many ways, applying himself to divers men in divers manners, as it seems good unto himself, and as men’s infirmities do require (c.f. John 3).
External evidences not necessary for faith in the Bible as God’s Word
And here we be to observe, that there is no absolute necessity of this secondary kind of argument, which is external and less principal, to beget faith in us; for it ought to suffice us, if the Spirit teach us only by God’s word. But to help our weakness the same Spirit adds the other secondary kind of argument, as Christ plainly teaches us (John 5), where he saith, the testimony of John Baptist concerning him was not simply necessary, but that God so provided to help their weakness and unbelief; “John gave testimony to the truth, hut I desire not the testimony of man. Nevertheless, these things I speak, that ye may be saved” (John 5:33). And that John’s testimony was but a secondary argument only, and that Christ’s own record of himself was the first, he shows plainly in the words following, “But I have a greater witness than the witness of John: for the works which the Father hath given me to finish, the same works that I do, bear witness of me that the Father sent me.” (John 5:36). And this is our judgment concerning this argument, whereby we prove the Scripture to be the word of God, and our answer to the question, wherefore it is so as we avouch it.
see also WLC Q. 4 – What causes us to believe the Scriptures? by Gregory Moeck.