An epistle is an apostolic letter that carries the authority of Scripture, addressed to specific churches or individuals but preserved by the Holy Spirit for the instruction of all believers across all ages. The NT epistles constitute the primary doctrinal and ethical framework of the Christian faith — from Paul's exposition of justification in Romans, to John's declarations of Christ's deity in 1 John, to Peter's call to suffering patience. They are not mere correspondence; Peter explicitly called Paul's letters "Scripture" (2 Pet 3:16). The epistles are the God-breathed working out of what the Gospels record — doctrine drawn from the life, death, and resurrection of Jesus, applied to the life of the church. To read the epistles is to sit in the classroom of the apostles.
EPISTLE, n. [L. epistola; Gr. epistolē.] A letter. The word is chiefly used as a title or denomination of the letters of the apostles; as, the epistles of Paul; the general epistles of Peter, John, and Jude. The word letter is now used for private communications.
• 2 Peter 3:16 — "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 Timothy 3:16–17 — "All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness."
• 1 Thessalonians 5:27 — "I put you under oath before the Lord to have this letter read to all the brothers."
• Colossians 4:16 — "When this letter has been read among you, have it also read in the church of the Laodiceans."
Modern scholarship has systematically attempted to undermine the authority of the NT epistles by questioning their authorship (e.g., claiming the Pastoral Epistles were written by pseudo-Pauline authors centuries later), their historical reliability, and their cultural applicability. The tactic is consistent: strip the epistles of apostolic authority, then reduce their commands to "culturally conditioned" advice that modern readers can discard. Once Paul is not really Paul, his instructions on gender, sexuality, church order, and doctrine become negotiable. But if the epistles are God-breathed — as the church has always affirmed — then they remain authoritative regardless of cultural discomfort. The living, active Word of God does not expire.