On the Unity of the Catholic Church 1

Since the Lord warns us and says, "You are the salt of the earth," and since he bids us be simple toward innocence and yet, with our simplicity, prudent, what else befits us, dearest brothers, than to be on our guard, and, watching with anxious heart, both to understand and to beware of the snares of the crafty enemy, lest we, who have put on Christ, the wisdom of God the Father, should seem less wise in guarding our salvation? For it is not persecution alone that is to be feared, nor those things that advance by open attack to overthrow and cast down the servants of God. Caution is easier where the danger is plain, and the mind is prepared for the contest in advance when the adversary declares himself. The enemy is more to be feared and guarded against when he creeps up secretly, when, deceiving under the image of peace, he slithers in by hidden approaches, whence he has also received the name of serpent. This is always his cunning; this is his blind and lurking deceit for entrapping man. So from the very beginning of the world he deceived, and, flattering with lying words, he beguiled the inexperienced soul through its unwary credulity. So, trying to tempt the Lord himself, he approached secretly, as if to creep up again and deceive; yet he was understood and beaten back, and therefore overthrown, because he was recognized and exposed.