It is an interesting secret, which emerges from the careful study of Catholic doctrine, as it has been articulated through the centuries. If we want to understand the Devil, that is the first place to look. The Church is the expert on demonic activity, having been in active competition with the infernal powers all this time. She is kept on her toes as their principal target. Until recently, she spoke with one clear voice, the words of Our Saviour, and indeed, were it not for divine assistance she would have succumbed to the satanic service, long long ago.
A copy of the fifth edition of the Essais with Montaigne's own "C" additions in his own hand exists, preserved at the Municipal Library of Bordeaux (known to editors as the "Bordeaux Copy").  This edition gives modern editors a text dramatically indicative of Montaigne's final intentions (as opposed to the multitude of Renaissance works for which no autograph exists). Analyzing the differences and additions between editions show how Montaigne's thoughts evolved over time. Remarkably, he does not seem to remove previous writings, even when they conflict with his newer views.