Sola scriptura is a metatheological doctrine held by certain Protestants and essentially consisting of two claims:

• All theological and ethical claims must be based on Scripture.
• No man's interpretation of Scripture is more authoritative than any other's.

The primary problem with 'sola scriptura' is that neither of those two claims are taught in Scripture, so 'sola scriptura' fails its own test. The second major problem with 'sola scriptura' is that it is unknown in Church history for 1,500 years. Even from the very earliest records of Church history we find a living Magisterium of bishops. The third major problem with 'sola scriptura' is that it makes each man his own ultimate authority, and thus leads to endless fragmentation of the Church, as the history of Protestantism clearly testifies. The fourth problem with 'sola scriptura' is that Scripture itself teaches that both the Church and the Apostolic Tradition have authority. The fifth problem with 'sola scriptura' is that Scripture itself does not tell us which books belong to the canon of Scripture, and thus the very existence of Scripture depends upon the authority of the bishops of the Church (i.e. the Magisterium).