Sola fide

Justificatio sola fide (or simply sola fide), meaning justification by faith alone, is a soteriological doctrine in Christian theology commonly held to distinguish the Lutheran and Reformed traditions of Protestantism, among others, from the Catholic, Eastern Orthodox, Oriental Orthodox, Assyrian and Anabaptist churches. The doctrine asserts that it is on the basis of faith alone that believers are made right of sin (such as their transgressions of divine law); and not on the basis of what Paul the Apostle calls "works of the law", which sola fide proponents interpret as including not only moral, legal or ceremonial requirements but any good works or "works of charity."

This forgiveness is known as "justification". In classical Lutheran and Reformed theologies, works are seen as crucial evidence of faith, but the works themselves do not determine salvation. In contrast, Methodist doctrine affirms a belief in justification by faith that offers God's forgiveness, but holds that holy living with the goal of Christian perfection (sanctification) is essential for salvation. Anabaptist theology categorically rejects the Lutheran and Reformed doctrine of sola fide, and instead emphasizes a "faith that works"; Anabaptists teach that "justification begun a dynamic process by which the believer partook of the nature of Christ and was so enabled to live increasingly like Jesus."

The doctrine of justification by faith alone and the role of repentance has been interpreted differently by different Protestants, causing multiple controversies such as: the Antinomian Controversy, the Majoristic controversy, the Marrow Controversy, and the Lordship salvation controversy.