When I was a kid in the Bible Belt, religious folks explained to me that the Bible was true because it said so, right in a Pauline letter to Timothy. You know the passage: "All Scripture is inspired by God and profitable for teaching, for reproof, for training in righteousness; that the man of God may be adequate, equipped for every good work." 2 Timothy 3:16-17. To the fundamentalists who tried to instruct me, the passage itself was Scripture, self authenticating. The passage applied to the whole Bible as they knew it.
Yet, just before this passage, Paul, or someone writing as Paul, refers to "the sacred writings" that Timothy has known "from childhood". Clearly, the author was not referring to his own letter as Scripture. Moreover, Paul or Pseudopaul as the case may be wrote letters before the Gospels were written, so he couldn't have meant the Gospels, or Acts, or the Apocalypse. He couldn't have meant any of the New Testament.
Scripture clearly refers to some part of the Old Testament as "sacred writings" which are efficacious for certain purposes. Nowhere in tis passage does Paul or his impostor claim that Scripture is a law book or a history book, only that is inspired by God and useful to equip the man of God. Perhaps the letters of Paul were inspired by God in some sense and are useful. Perhaps someone right now is writing something under the influence of the Spirit and this will be useful. Some sermon to be delivered this Sunday may well be God breathed and useful for a man of God.