Soli Deo gloria is the motto that grew out of the Protestant Reformation and was used on every composition by Johann Sebastian Bach. He affixed the initials SDG at the bottom of each manuscript to communicate the idea that it is God and God alone who is to receive the glory for the wonders of His work of creation and of redemption. At the heart of the sixteenth-century controversy over salvation was the issue of grace.
It was not a question of man’s need for grace. It was a question as to the extent of that need. The church had already condemned Pelagius, who had taught that grace facilitates salvation but is not absolutely necessary for it. Semi-Pelagianism since that time has always taught that without grace there is no salvation. But the grace that is considered in all semi-Pelagian and Arminian theories of salvation is not an efficacious grace. It is a grace that makes salvation possible, but not a grace that makes salvation certain.