Effort in Sanctification? What Says Westminster?

“Justification is monergistic.  Sanctification is synergistic.”  Perhaps you’ve heard that explanation of the relationship between justification and sanctification.  What do you think of it?  At first and for a long time, I found it helpful.  I first heard it from RC Sproul (full disclosure:  I love RC Sproul.  I’m Reformed today – and a pastor …