Soli Deo Gloria

Bach inscribed Soli Deo Gloria (Glory to God alone) — abbreviated S.D.G. — on the manuscripts of his church compositions throughout his career. The phrase is one of the five soli of Lutheran theology, expressing the conviction that God alone deserves ultimate honour. For Bach, it was a professional and devotional signature: a reminder that the music was not for the composer's glory but as an offering to God. It appears on cantatas, the Mass in B minor, and the Passion settings.