Martin Luther set the Reformation in motion in 1517, attacking the corruption in much of the medieval Catholic Church.
He set out a simpler religion that was based on scripture and the personal faith of the individual believer.
He proclaimed the doctrine of sola fide.
Sola fide
A Latin term meaning 'by faithalone'. It refers to the belief of Martin Luther and of many Protestants that justification is by faith alone and not by works.
He taught that the faith of the believer is passive; justification comes by what God achieves through the atoning death of Jesus.
For Luther, good conduct was the expression of a person's faith, but it had no saving value whatsoever.