The question has the history backwards. Catholics did not add seven books; the Reformers removed them. Those seven — Tobit, Judith, Wisdom, Sirach, Baruch, and First and Second Maccabees, along with portions of Esther and Daniel — stood in the Greek Old Testament (the Septuagint) that the Apostles themselves quoted, sat in the Christian Bible for roughly 1,500 years, and were listed as Scripture by the early councils. They were pulled out of the Old Testament only in the 1500s. So the real question is not why the Catholic Old Testament is longer; it is who made the Protestant one shorter, and on whose authority.

When the New Testament quotes the Old, it usually quotes the Septuagint — the very collection that included these books. And its writers plainly knew them: the great roll-call of faith in Hebrews salutes those who “were racked, not accepting deliverance, that they might find a better resurrection” (Hebrews 11:35) — an unmistakable tribute to the martyred mother and her seven sons in 2 Maccabees 7. A book a New Testament author treats as sacred history is not an “addition.”

The Church also settled the list early and repeatedly. A Roman council in 382, then Hippo (393) and Carthage (397), enumerated the canon — these books included — and St. Augustine’s own catalogue names “Tobias… Judith, and the two books of Maccabees” among the Scriptures.1 The same canon was reaffirmed at the Council of Florence in 1442, a full century before Trent. Honesty requires a concession: some Fathers — St. Jerome chief among them — preferred the shorter Hebrew list and ranked these books lower, so there was real discussion. But Jerome translated them for the Vulgate all the same and deferred to the Church, whose conciliar judgment consistently kept them. Trent (1546) did not invent the canon; it dogmatically reaffirmed the one Christendom had used all along, precisely because it was now being denied.

Which exposes the deeper issue: by what authority does anyone fix the table of contents? The Reformers’ own criterion is revealing — Luther, on his theological judgment, also wished to demote James, Hebrews, Jude, and Revelation to a lesser rank. A canon trimmed to fit a doctrine is not a canon received; it is a canon edited. The Catholic answer is that the same Church Christ founded — not a 16th-century reformer, and not private judgment2 — recognized and handed down the books, Old and New Testament together. The full history of the canon traces every step.