Justification and sanctification

Trent solidified the principal doctrinal division of the Reformation when it declared that although justification starts as a completely free gift from God, there is a need for individuals to respond cooperatively, and so a positive role for free will. Whereas Luther's justified sinner remained just that, Trent taught that intrinsic to justification was an individual actual transformation through grace into a more perfect disciple of Christ.

Peter Marshall, The Reformation (A Very Short Introduction), OUP 2009, p. 45