There's a scene from the movie Dirty Rotten Scoundrels where the main character, Ruprecht, barges in a dinner party making a big scene. When I think of that scene, that what's I believe Luke 15 looks like. Jesus barging into a meeting where the religious elite are dicussing "those people" that Jesus hangs out with - sinners and tax collectors. Instead of indulging them, He gives them a master class on grace; and I believe what He teaches us, is that grace isn't a checklist that determines if you are good enough. Maybe grace looks more like a house party where everyone is welcome.