I have a few a priori beliefs. They include: God exists, He has revealed Himself to us in the Bible (which consists of the 66 books we have today). . . . . As for the canonicity question, I'm unlikely to ever go into in much detail. Here's the short version: for me, the belief that the 66 books we have constitute God's inspired word is a priori. It is one of the givens I build all my other doctrine on. Is perfect text preservation an a priori for you?
I want to frame this correct. I'm taking it from part of what he stated: "the belief that the 66 books we have constitute God's inspired word is a priori." Before we can even understand the nature of this belief, we have to understand what a priori is all about. Before we explore that portion of this consideration, I would first agree that a belief in God is a priori. Why do I believe that? Because that's what the Bible says. Romans 1:18 says that unbelievers "hold the truth in unrighteousness," that is, they suppress the truth. The next verse (v. 19) goes on to say that God has already shown Himself to them. And, of course, they just suppress that truth rather than receive it. So I agree with this commenter about an a priori belief in the existence of God.
A Priori and A Posteriori
A priori is a Latin phrase, of course, and it denotes the foundations upon which something can be known. It is in contrast to a posteriori, the latter something knowable on the basis of experience. A priori is known independent of experience. Someone who believes something a priori would necessarily have some reason to justify that something is true that is not derived from experience. When we say "experience" we don't mean only the experience of the one knowing. For instance, I don't have to experience the distance from the sun in order to know or believe that it is 93 million miles from the earth. I can depend on others' measurements, their experience, in order to know this to be true. This is not a priori knowledge.
Scriptural doctrine is not a priori knowledge. Believers rightly consider the Bible to be sufficient empirical evidence for faith and practice. So we should consider legitimate arguments from God's Word as a categorically reliable experience for justifying a proposition.
A claim that one knows or believes a particular proposition a priori, like the existence of a 66 book canon of Scripture, without having any epistemic reason of support, is and should be susceptible to very serious skepticism. It is not enough simply to claim that we have a 66 book canon---that is akin to sheer guesswork. One is obliged to shed some light on the reliability of the proposition of a 66 book canon. The absence of experience or rational insight does not insist nor should it encourage a priori argumentation.
Lines of Reasoning
Two major lines of reasoning have dominated the argument about the canonicity of Scripture---what are now referred to as a Roman Catholic view and a Protestant view. Both actually make their argument from the Bible. The Protestants have criticized the Roman Catholics for their circular reasoning, which goes something like this: the Bible says that the church sustains and safeguards Scripture, so the church determines which books are canonical. With this attack on circularity, the Protestants must defend against their own. The Protestants wished also to affirm the Bible as what ruled their belief about the Bible, maintaining sole scriptura as the source of authority.
Richard Muller in his Post-Reformation Reformed Dogmatics refers to the work of Dutch Protestant Leonard Van Rijssen in his Summa Theologiae Elencticae Completa (1692). Muller explains and translates (pp. 387-388):
In the first case, Scripture itself demonstrates by its marks or qualities "such as light and splendor," that it is worthy of belief; in the second, it is the Spirit who, as noted in Luke 24:45, "opened" the understanding of the disciples, and who, by implication, opens the understanding of believers to the truth of the Scriptures; in the third, it is the church, used by God in the preservation and communication of the truths of Scripture. If, therefore, Scripture is said to be proven worthy of belief by the Spirit, the statement refers to the Spirit as the efficient cause of the belief. If, however, we ask on what ground we believe that the Spirit testifying within us is the Holy Spirit, the answer is that we know by the marks of the Spirit revealed in Scripture. As for the objective authority of Scripture, it is to be grounded on the Scripture itself, understood as self-authenticating. Nor, comments Riissen, does it hold against the Protestant argument to claim that the church is the authority that indicates which books are canonical and which are not---for John the Baptist indicated the identity of the Messiah, but the Messiah's authority surely did not rest on John the Baptist!---"it is one thing to discern and declare the canon, quite another to constitute it and make it authentic."
Rijssen makes a strong argument for an a posteriori belief in canonicity. The church does not have authority over Scripture any more than John the Baptist had authority over Jesus. The church identifies the canon and John the Baptist identifies Jesus. Rijssen also debunks the idea that church acceptance and recognition are church authority (in contradiction to such modern writers such as Ridderbos, who advocate a priori belief in a sixty-six book canon). The church doesn't have authority over Scripture, but Scripture itself provides that basis for its own canonicity. Believers will be guided by the Spirit to the authoritative New Testament books. Muller also refers (p. 394) to Musculus (born in 1497), 1560 work, Loci Communes Sacrae Theologiae on canonicity:
[T]he apocryphal or "hidden" books belong outside of the canon, inasmuch as they contain common teachings arising from "the spirit of man" more than from the Spirit of God---and they also include "some points not fully in agreement with the canonical Scriptures."
The Callican Council of 1559 was the first Protestant council of the French Protestants. In their Gallican Confession, they wrote:
We know these books to be canonical, and the utterly certain rule of our faith, not so much by the universal agreement and consent of the church as by the testimony and the inward persuasion of the Holy Spirit, who enables us to discern them from other churchly books.
His "theological attainments" procured Edward Leigh a seat in the Westminster Assembly, one of which was his five volume A Treatise of the Divine Promises (1633). He wrote (pp. 42-43):
From the Divine flows the Canonical authority of the Scripture. The books of Scripture are called Canonical books . . . . because they were put into the Canon by the Universal Church.
Of course, those who read here know I don't support the doctrine of the universal church as Leigh did, but the point is the same in that saints recognized that the Holy Spirit guided believers to accept the Canonical Books, something they were continuing to do in the 17th century. For this to be an merely a priori as our commenter asserted, it would seem that would have received no further attention past the first few centuries.
In something more modern (1984), Brevard S. Childs, in his The New Testament as Canon: An Introduction, wrote (p. 33):
It is hard to escape the impression that the later expositions of the criteria of canonicity were, in large part, after-the-fact explanations of the church's experience of faith in Jesus Christ which were evoked by the continued use of certain books.
Roger Nicole wrote a title to an entire section of his article in the Journal of the Evangelical Theological Society in June 1997 (p. 204):
The Witness of the Holy Spirit Given Corporately to God's people and Made Manifest by a Nearly Unanimous Acceptance of the NT Canon in Christian Churches
Nicole continues then:
There is a notable parallel here with the establishment of the OT canon. God entrusted his OT oracles to the Jews (Rom 3:2), and they were providentially guided in the recognition and preservation of the OT. Jesus and the apostles confirmed the rightness of their approach while castigating their attachment to a tradition that was superimposed on the Word of God (Matt 15:1–20; Mark 7:1–23). God entrusted his NT oracles to his people in the churches, and they are nearly unanimous in the recognition of the NT canon. . . . The consensus of churches on the NT is an index and evidence of the Holy Spirit’s guidance. The Holy Spirit is the moving authoritative force.
Keith A. Matheson wrote recently (2001) in his book The Shape of Sola Scriptura (p. 319):
But although the Church is a fallible authority, [scriptural teaching] does not assert that this fallible Church cannot make inerrant judgments and statements. In fact, in the case of the canon of the New Testament, adherents of [scriptural teaching] would confess that the fallible Church has made an inerrant judgment. But do we believe this because a particular Church tells us so? No, we believe this because of the witness of the Holy Spirit, which was given corporately to all God's people and has been made manifest by a virtually unanimous receiving of the same New Testament canon in all of the Christian churches. This is not an appeal to subjectivism because it is an appeal to the corporate witness of the Spirit to whole communion of saints. The Holy Spirit is the final authority, not the Church through which He bears witness and to which He bears witness.
Saying You "Just Believe" There Are 66 Books A Priori
Why do you believe there are 66 Books in the Bible and not 65 or 67? "I just do." Do you have a reason? "No. My faith is a priori in the case of 66 Books like it is with my belief in the existence of God." Faith a priori in the existence of God, as we established before in Romans 1, is a belief taught in Scripture. To say that our faith in 66 Books is the same would be the same as my saying that I know a priori that the physical ark of the covenant, that was carried by Israel in the wilderness, still physically exists. We don't just "know" that there are 66 Books without any kind of previously written basis for that.
To know the 66, we know that based on something that occurred before. We had Scripture that would provide the criteria. There is Scripture with which to compare. There is the Holy Spirit, who indwells us, because we heard Scripture, who testifies to us. This is not a priori faith. This faith comes from evidence (Hebrews 11:1-3).
Verses from Scripture to Consider
John 16:13---Howbeit when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will shew you things to come.
John 17:17---Sanctify them through thy truth: thy word is truth.
John 17:8---For I have given unto them the words which thou gavest me; and they have received them, and have known surely that I came out from thee, and they have believed that thou didst send me.
1 Corinthians 2:14-16---But the natural man receiveth not the things of the Spirit of God: for they are foolishness unto him: neither can he know them, because they are spiritually discerned. But he that is spiritual judgeth all things, yet he himself is judged of no man. For who hath known the mind of the Lord, that he may instruct him? But we have the mind of Christ.
1 John 5:6---And it is the Spirit that beareth witness, because the Spirit is truth.
How It Works with Books
The Holy Spirit wrote all the Books. The Holy Spirit knows what the Books are. He knows there are 66. He knows which 66 are the right 66. The Holy Spirit also indwells all believers. The Holy Spirit leads and guides believers. That is the Holy Spirit working through them. It is the Holy Spirit doing good through them. As the Books are completed, the Person of the Holy Spirit tells believers what His Books are. By means of believers' agreement, by means of their recognition of which Books are actually God's Books, believers know what are His Books. This is not believers having authority over God's Books, but God the Holy Spirit having authority over His believers.
At times since believers agreed on what the right, correct Books were, the 66 and which 66, the right 66 have been challenged. Some have said there are others that are Books in addition to those 66. Some have said that some of the 66 are not actually right and correct. Because of these challenges, believers have continued to agree and recognize which 66 were the right and correct 66. These challenges have occurred in every century. Believers have kept agreeing and recognizing through the Holy Spirit working in and through them in order to sustain or maintain those 66 right and correct Books.
How It Works with Words
Just to start, the Bible itself, the evidence, the experience, believers need (a posteriori), says something about guidance to Words and reception of Words for believers. The Bible doesn't even say anything per se about Books regarding canonicity. It does say something about Words. However, within the more detailed guidance of the Holy Spirit of believers to Words, He will also guide to Books. If someone is not going to question Books, then He should not question Words, because Words are where the guidance and preservation and sustaining actually are. With that in mind, the following is how it works.
The Holy Spirit wrote all the Words. The Holy Spirit knows what the Words are. He knows the exact ones because He wrote them and He knows everything. He knows which Words are the right Words. The Holy Spirit also indwells all believers. The Holy Spirit leads and guides believers. That is the Holy Spirit working through them. It is the Holy Spirit doing good through them. As the Words are completed, the Person of the Holy Spirit tells believers what His Words are. By means of believers' agreement, by means of their recognition of which Words are actually God's Words, believers know what are His Words. This is not believers having authority over God's Words, but God the Holy Spirit having authority over His believers.
At times since believers agreed on what the right, correct Words were, the exact number of Words and which Words, the right Words have been challenged. Some have said there are others that are Words in addition to those Words. Some have said that some of the Words are not actually right and correct. Because of these challenges, believers have continued to agree and recognize which Words were the right and correct Words. These challenges have occurred in every century. Believers have kept agreeing and recognizing through the Holy Spirit working in and through them in order to sustain or maintain those right and correct Words.
Conclusion
Some might say, "Well, God will lead to Books, but He won't lead to Words." Or, "Believers can know what the Books are, but they can't obviously know what the Words are." Why? God gave the exact Words to individual men and we trust that. Some will say, it is not a matter of whether He is able, but whether Scripture says what He would do. But those same people will say that there are 66 Books. Why? How do they know that?
The same Spirit indwells every believer and all believers. Their testimony to the Words of Scripture are powerful. What they have done should be considered. God's Word is perfect. God's Word is complete. God inspired individual Words for believers to live by. Let's trust the Lord to guide us into all truth, into all the Words that He inspired. The position I'm explaining here is the position that has been taken by believers. We read it in history during the 17th century and since where we have much record of what Bible-believers said and wrote. This is no private interpretation. God is pleased by faith. May He continue to be honored by ours today.