The Five Solas are the Reformation's five-word answers to five foundational questions of the Christian faith. Sola Scriptura ("Scripture alone") answers "By what authority?" — the Bible alone is the final, sufficient rule of faith and practice. Sola Fide ("faith alone") answers "By what means?" — we are justified by faith alone, not by faith plus works. Sola Gratia ("grace alone") answers "Through whose merit?" — salvation is by God's grace alone, not earned by any human merit. Solus Christus ("Christ alone") answers "Through what mediator?" — Christ alone is the mediator between God and man, not priests, saints, or Mary. Soli Deo Gloria ("to God alone be the glory") answers "To what end?" — all of salvation is for God's glory alone, not the enhancement of any human reputation or institution. Each Sola excludes an error: Sola Scriptura excludes tradition and papal decrees as equal authorities; Sola Fide excludes works-righteousness; Sola Gratia excludes human contribution to salvation; Solus Christus excludes all other mediators; Soli Deo Gloria excludes any glory for self. Together they form the spine of Protestant orthodoxy and the dividing line between the Reformation and Rome.