"This doctrine [justification by faith] is the head and the cornerstone. It alone begets, nourishes, builds, preserves, and defends the church of God; and without it the church of God cannot exist for one hour…. For no one who does not hold this article – or, to use Paul's expression, this 'sound doctrine' (Titus 2:1) – is able to teach aright in the church or successfully to resist any adversary . . . this is the heel of the Seed that opposes the old serpent and crushes its head. That is why Satan, in turn, cannot but persecute it...Whoever departs from the article of justification does not know God and is an idolater . . . For when this article has been taken away, nothing remains but error and hypocrisy."- Luther
