“Sola Scriptura” is the doctrine proclaiming that the Bible is ultimate source of truth. Often it is thought of as a “Protestant” doctrine, yet, from the beginning of church history, great Christian thinkers have realized that it is the primary source of truth in the Christian Church.
Tradition and wisdom may also attest to truth, but only the Scriptures speak with infallible authority.
“There is, brethren, one God, the knowledge of whom we gain from the Holy Scriptures, and from no other source. For just as a man, if he wishes to be skilled in the wisdom of this world, will find himself unable to get at it in any other way than by mastering the dogmas of philosophers, so all of us who wish to practise piety will be unable to learn its practice from any other quarter than the oracles of God.
Whatever things, then, the Holy Scriptures declare, at these let us took; and whatsoever things they teach, these let us learn; and as the Father wills our belief to be, let us believe; and as He wills the Son to be glorified, let us glorify Him; and as He wills the Holy Spirit to be bestowed, let us receive Him. Not according to our own will, nor according to our own mind, nor yet as using violently those things which are given by God, but even as He has chosen to teach them by the Holy Scriptures, so let us discern them.” (Against the Heresy of One Noetus, 1-4, 7-9)
“They [heretics] gather their views from other sources than the Scriptures. We have learned from none others the plan of our salvation, than from those through whom the Gospel has come down to us, which they did at one time proclaim in public, and, at a later period, by the will of God, handed down to us in the Scriptures, to be the ground and pillar of our faith.
For they [the Apostles] were desirous that these men should be very perfect and blameless in all things, whom also they were leaving behind as their successors, delivering up their own place of government to these men; which men, if they discharged their functions honestly, would be a great boon to the Church, but if they should fall away, the direst calamity. Proofs of the things which are contained in the Scriptures cannot be shown except from the Scriptures themselves.” (Against Heresies, 1:8:1, 3:1:1, 3:3:1, 3:12:9)