The three principles which have influenced us to undertake a discussion of the present theme--and of the truth of which we are profoundly convinced--are the following: I. THAT INFIDELITY PRESENTS A SYSTEMATIC AND HARMONIOUS HISTORY. Our customary view of error is, that its history is disjointed, rendered so by the ardent, but unsteady, labors of the doubters of all periods since the origin of Christianity. We have ignored the historical movement of skepticism. Even the storms have their mysterious laws. The work of Satan is never planless. He adapts his measures to the new dangers that arise to threaten his dominion. The analogy between the Rationalism of to-day and the infidelity of past ages is so striking that we can with difficulty recognize the interval of centuries. We see the new faces, but the foes are old. Rationalism has repeatedly varied its method of attack; but if we follow the marches of its whole campaign we shall find that the enemy which stands at our fortress-gate with the _Essays and Reviews_ and _Notes on Pentateuch and Joshua_ in hand, is the same one that assailed Protestant Germany with the Accommodation-theory and the _Wolfenbuettel Fragments_. II. A HISTORY OF A MISCHIEVOUS TENDENCY IS THE VERY BEST METHOD FOR ITS REFUTATION AND EXTIRPATION. We can learn the full character of the good or evil of any abstract principle only by seeing its practical workings. The tree is known by its fruits. Rationalism may be of evil character, but we must see the results it has produced,--the great overthrow of faith it has effected, and its influence upon the pulpit and press of the countries invaded by it, before we can comprehend the vastness of our danger. An enumeration of the evil doings of a public enemy is the best plan to forestall his future misdeeds. We are not to judge Rationalism by its professions. The question is not, What does it wish? At what does it aim? or, What is its creed? But the true way to measure, understand, and judge it, is by answering the inquiry, _What has it done?_ Its work must determine its character. This work has been most injurious to the faith and life of the church, and its deeds must therefore be its condemnation. There are those who say, "Tell us nothing about skepticism; we know too much about it already." Would it be a prudent request, if, before penetrating the jungles of Asia, we should say, "Tell us nothing of the habits of the lion"; or, before visiting a malarious region of Africa, we should beg of the physician not to inform us of the prevalent fever and its appropriate remedy? Forewarned is forearmed. We are surrounded by Rationalism in many phases; it comes to us in the periodical and the closely-printed volume. Even children are reading it in some shape or other. Shall we know its danger; then we must know its deeds.