Listen to Aquinas

Nevertheless sacred doctrine makes use of these authorities [Church Fathers and tradition] as extrinsic and probably arguments, but properly uses the authority of canonical Scriptures as a necessary demonstration and the authority of the doctors of the Church as one that may properly be used, yet merely as probable. For our faith rests upon the revelation made to the apostles and prophets, who wrote the canonical books, and not on the revelations (if any such there are) made to other doctors—Thomas Aquinas as quoted in Why Church History Matters, page 44