Now, this requires a profound knowledge of Christianity, which is not attainable by private judgment from the Scriptures, or outside of the infallible authority of the church with which the revelation of God, the revealed word, is deposited as its guardian and interpreter. M. Migne, indeed, admits some treatises written by Protestants into his collection of works he has published under the title of _Evangelical Demonstration_, which are not without their merit, but are valuable only on certain points, and on those only so far as they rest on Catholic principles and use Catholic arguments. Christianity being supernatural, a revelation of the supernatural, it, of course, while addressed to natural reason, cannot be determined or defined by natural reason, and can be determined or defined, preserved or 15 presented, in its purity and integrity, only by an authority supernaturally instituted and assisted for that very purpose. Even what the author calls natural theology, since it is only initial, like the cosmos, is incomplete, and, though not above natural reason, needs the supernatural to fulfil it, and therefore the supervision and control of the same supernaturally instituted and assisted authority to preserve it from error, from a false development, or from assuming a false direction, as we see continually occurring with those who have not such an authority for guide and monitor. Hence, even in matters not above the province of natural reason, natural reason is not a sufficient guide, or else whence come those errors of the Positivists in the purely scientific order the learned doctor combats with so many words, if not thoughts--with so many assertions, if not arguments? Hence, since Protestants have no such authority, and make it their capital point to deny that anybody has it, it follows that they are unable to present any authoritative statement, or any statement at all which an unbeliever is bound to respect, of what Christianity really is, or what is the authentic meaning of the term. They can give only their private views or opinions of what it is, and these the unbeliever is not bound to place in any respect above his own, especially since they vary with every Protestant sect, and, we may almost say, with every individual Protestant who thinks enough to have an opinion of any sort. Even if they borrow Catholic traditions, Catholic principles, and Catholic doctrines and definitions, these in their hands lose their authoritative character, and become simply opinions resting on private reason. They can present as Christianity nothing authentic to be defended by the Christian, or to be accepted or rejected by the unbeliever. Clearly, then, Protestants are in no condition to manage apologetics with acute, scientific, and logical unbelievers; and if we wanted any proof of it we could find it, and in abundance, in the volume before us.