"...being confident of this very thing, that He who has begun a good work in you will complete it until the day of Jesus Christ; [Philippians 1:6]Does Philippians 1:6 guarantee progressive sanctification? I had always grown up with this view. And even today, I can hardly listen to Christian radio, a sermon, or just conversation with fellow believers and go very long without hearing Philippians 1:6 cited in this very sense. In fact, at the local fellowship I attend, our pastor cited this verse in this very sense this last Sunday.
The classic interpretation is that the "good work" that God has begun in the individual believer (salvation) will continue and carry on to culmination until the day of Christ. In essence, sanctification is progressive. And, God is bringing this to fruition in the life of the individual believer.
It was not until college, that some other brothers challenged my view on Philippians 1:6. And, as I looked and thought more about this text over the years, I have come to the position that there is definitely another viable interpretation. While it is certainly true that God is the author of our salvation from A to Z (justification, sanctification and ultimately glorification), I am not sure that this verse teaches that idea. It all hinges on what Paul is referring to by the "good work" that God has begun.
Check out this article for a more technical discussion on why there is quite possibly a better interpretation --> Phillipians 1:6