AKA Biblical Authority, Bible Authority, Authority of the Bible
The Bible has authority because it is divinely authorized. 2 Timothy 3:16: All Scripture is inspired by God and beneficial for teaching, for rebuke, for correction, for training in righteousness.
This refers to the whole Old Testament, and extension of the claim for the New Testament is neither explicitly stated nor merely implied. The New Testament contains indications that its content was to be viewed and was viewed as no less authoritative than the Old.
J. Gresham Machen wrote that belief in the central message of the Bible is core to Christianity, not belief in biblical inerrancy. But he believed the whole Bible is to be considered "the seat of authority." He was convinced the doctrine of inerrancy avoids instability in expounding authoritative doctrine and morals. He insisted that a "mediating" view of the Bible is not tenable. "Modernists" who claim to honor the authority of Jesus rather than the Scripture contradict His teaching since Jesus held a high view of Scripture.
(The Origin of the Bible: Newly Updated by F. F. Bruce, J. I. Packer, Philip W. Comfort, and Carl F. H. Henry, 2020. Page 14-22.)
New Testament Authority
The principle determining recognition of the authority of the canonical New Testament writings was established within the content of those writings themselves. There are repeated exhortations for public reading of the apostolic communications.
I put you under oath before the Lord to have this letter read to all the brothers. (1 Thessalonians 5:27)
The epistles recognizes themselves as the word of God.
And we also thank God constantly for this, that when you received the word of God, which you heard from us, you accepted it not as the word of men but as what it really is, the word of God, which is at work in you believers. (1 Thessalonians 2:13)
If anyone thinks that he is a prophet, or spiritual, he should acknowledge that the things I am writing to you are a command of the Lord. (1 Corinthians 14:37)
The revelation of Jesus Christ, which God gave him to show to his servants[a] the things that must soon take place. He made it known by sending his angel to his servant John, who bore witness to the word of God and to the testimony of Jesus Christ, even to all that he saw. (Revelation 1:1-2)
(The Origin of the Bible: Newly Updated by F. F. Bruce, J. I. Packer, Philip W. Comfort, and Carl F. H. Henry, 2020. The Canon of the New Testament by Milton C. Fisher. Page 69)
Paul's writings are catalogued with "the rest of the Scriptures"
And count the patience of our Lord as salvation, just as our beloved brother Paul also wrote to you according to the wisdom given him, as he does in all his letters when he speaks in them of these matters. There are some things in them that are hard to understand, which the ignorant and unstable twist to their own destruction, as they do the other Scriptures. (2 Peter 3:15-16)
Under the heading of "Scripture," 1 Timothy 5:18 cites Luke 10:7 alongside Deuteronomy 25:4, implying an equivalence. The book of Revelation claims divine origin (1:1-3) and employs the term "prophecy" in the Old Testament sense (22:9-10,18). The apostles did not distinguish their spoken and written teaching but expressly declared their inspired proclamation to be the Word of God from the Holy Spirit.
(The Origin of the Bible: Newly Updated by F. F. Bruce, J. I. Packer, Philip W. Comfort, and Carl F. H. Henry, 2020. Page 14-22.)
Paul's letters were widely known
Peter's is a general letter. Also, in A.D. 95, Clement of Rome wrote to the Christians in Corinth using a free rendering of material from Matthew and Luke with strong influence from Hebrews and obvious familiarity with Romans and Corinthians. He also included reflections on 1 Timothy, Titus, 1 Peter, and Ephesians. These both indicate widespread knowledge of Paul's letters.
The church quickly accepted the New Testament as authoritative
By the beginning of the 2nd century, the New Testament was widely known and recognized as authoritative. The John Rylands papyrus indicates John was revered and copied as far as Egypt by A.D. 125, within 30-40 years of the apostle's death. There is also evidence all the Gospels and Pauline letters were known and used throughout the church within 30 years of John's death.
The authority of some of the smaller letters was questioned in some quarters for another 50 years, but this was only due to the uncertainty of their authorship in those locales. This demonstrates that acceptance was not imposed by councils but rather happening spontaneously through a normal response on the part of those who had learned the facts about authorship. In places where the churches were uncertain about the authorship or apostolic approval of certain books, acceptance was slower.
(The Origin of the Bible: Newly Updated by F. F. Bruce, J. I. Packer, Philip W. Comfort, and Carl F. H. Henry, 2020. The Canon of the New Testament by Milton C. Fisher. Page 69-70)
Threats to Biblical Authority
No Authority in the West
Western civilization is currently challenging authority on every level - parental authority, marital authority, political authority, academic authority, ecclesiastical authority, that of Scripture, the pope. Man's "coming of age" in rejecting divine authority and championing human autonomy and creative individuality is as old as Adam and Eve. It is sin, not philosophical gnosis.
Biblical authority is undermined by higher criticism and criticism of all forms and is coupled with stances on biblical inerrancy and biblical infallibility.
(The Origin of the Bible: Newly Updated by F. F. Bruce, J. I. Packer, Philip W. Comfort, and Carl F. H. Henry, 2020. The Authority of the Bible by Carl F.H. Henry. Page 13, 15, 20)
Culturally Dependent Interpretations of Scripture
Mediating scholars allow the culturally dependent teaching of the day to dismiss Paul's teachings on the position of women, homosexuality, and a regathering of Israel in Palestine as reflective of the rabbinic teaching of the time and evident of Paul's culturally limited perspective. Yes, biblical teaching coincides with Jewish tradition, but Jesus was critical of times when Hebrew tradition is elevated into a norm considered superior to or modifying and contravening Scripture. Paul was sharply critical of rabbinical tradition at times, too.
The culture of the day should not be allowed to undermine the Bible's authority. The Bible is not derived from mere tradition but it is God-breathed. Otherwise, how can you establish an objective criteria for distinguishing between apparently authoritative and unauthoritative apostolic doctrine?
(The Origin of the Bible: Newly Updated by F. F. Bruce, J. I. Packer, Philip W. Comfort, and Carl F. H. Henry, 2020. The Authority of the Bible by Carl F.H. Henry. Page 23)
Functional
The Scripture is an inner life-transforming stimulant, but its conceptual propositional authority is irrelevant. People with this view depart from the evangelical view that the authority of Scripture is concentrated in its disclosure of divinely revealed truths that constitute the rule of faith and morals. Divergent views of Scripture, no matter how conflicting and contradictory, are accepted equally.
Of course, if you reject the validity of biblical teaching in part, the whole Bible is rejected, and its transformative power is equal to any secular media.
(The Origin of the Bible: Newly Updated by F. F. Bruce, J. I. Packer, Philip W. Comfort, and Carl F. H. Henry, 2020. The Authority of the Bible by Carl F.H. Henry. Page 23-24)
Secondary and tertiary authorities blur the Bible's authority--apocryphal books, ecclesiastical tradition, and cultic interpretation.
(The Origin of the Bible: Newly Updated by F. F. Bruce, J. I. Packer, Philip W. Comfort, and Carl F. H. Henry, 2020. The Authority of the Bible by Carl F.H. Henry. Page 26)