The Lutheran Church is the oldest Protestant Christian tradition, dating back to the Protestant Reformation and the person of Martin Luther. Lutherans are those Christians who choose to accept Martin Luther's teachings. On October 31, 1517, Luther, a Catholic monk, posted his 95 Theses as a challenge to the doctrine and practices of the Roman Catholic Church, hoping to reform the practices he felt were inconsistent with scripture. When the conflict escalated to a distinct separation with the Roman Catholic Church, those who accepted Luther's reforms became "Lutherans." Based on Luther's own writings, Lutherans still uphold Luther's theological teachings such as sola scriptura (scripture as the primary authority for faith and life), justification by the grace of God alone, and salvation through faith in Christ alone. Luther's many theological ideas have since been collected into the Book of Concord, which is still an authority in Lutheran doctrine and practice. Because of its initial grounding in the Roman Catholic Church, Lutheran worship, more than many other Protestant traditions, has many elements similar to the Catholic style of worship. Lutheranism spread from Germany to most countries across the globe and has become one of the largest Protestant denominations.