Sinclair Ferguson gives a short history lesson on certain views of Protestant theology by the Roman Catholic church, and counters them with some reflections on Hebrews:
How would you answer? What is the greatest of all Protestant heresies? Perhaps justification by faith? Perhaps Scripture alone, or one of the other Reformation watchwords?
Those answers make logical sense. But none of them completes Bellarmine’s sentence. What he wrote was: “The greatest of all Protestant heresies is…”
I won’t spoil it. Go read the post to find out.