Sola scriptura (‘Scripture alone’) is one of the five ‘solas’ of the Reformation — the principle that Scripture is the sole infallible and final authority for Christian faith and practice. Against the Catholic claim that Scripture and Tradition together constitute the norm of faith, Luther insists that Scripture alone judges all tradition, councils, and papal decrees. The famous confrontation: at the Diet of Worms (1521 AD), Luther refuses to recant unless ‘convinced by Scripture and plain reason’ — ‘my conscience is captive to the Word of God.’ Sola scriptura is not the claim that Scripture is the only authority (Luther accepts reason, creeds, and tradition as subordinate authorities) but that Scripture is the final court of appeal. Critics note the problem: who interprets Scripture? The Reformation’s splintering into hundreds of denominations each claiming Scripture’s authority for contradictory positions is the practical consequence.