In what follows the Introduction, except in the setting there is nothing new. I trust there is nothing new. When I began to follow out these lines, I had no idea where they would lead me. I was prepared, nevertheless, at least for the time, to be loyal to the method throughout, and share with nature whatever consequences might ensue. But in almost every case, after stating what appeared to be the truth in words gathered directly from the lips of Nature, I was sooner or later startled by a certain similarity in the general idea to something I had heard before, and this often developed in a moment, and when I was least expecting it, into recognition of some familiar article of faith. I was not watching for this result. I did not begin by tabulating the doctrines, as I did the Laws of Nature, and then proceed with the attempt to pair them. The majority of them seemed at first too far removed from the natural world even to suggest this. Still less did I begin with doctrines and work downward to find their relations in the natural sphere. It was the opposite process entirely. I ran up the Natural Law as far as it would go, and the appropriate doctrine seldom even loomed in sight till I had reached the top. Then it burst into view in a single moment. I can scarcely now say whether in those moments I was more overcome with thankfulness that Nature was so like Revelation, or more filled with wonder that Revelation was so like Nature. Nature, it is true, is a part of Revelation--a much greater part doubtless than is yet believed--and one could have anticipated nothing but harmony here. But that a derived Theology, in spite of the venerable verbiage which has gathered round it, should be at bottom and in all cardinal respects so faithful a transcript of "the truth as it is in Nature" came as a surprise and to me at least as a rebuke. How, under the rigid necessity of incorporating in its system much that seemed nearly unintelligible, and much that was barely credible, Theology has succeeded so perfectly in adhering through good report and ill to what in the main are truly the lines of Nature, awakens a new admiration for those who constructed and kept this faith. But however nobly it has held its ground, Theology must feel to-day that the modern world calls for a further proof. Nor will the best Theology resent this demand; it also demands it. Theology is searching on every hand for another echo of the Voice of which Revelation also is the echo, that out of the mouths of two witnesses its truths should be established. That other echo can only come from Nature. Hitherto its voice has been muffled. But now that Science has made the world around articulate, it speaks to Religion with a twofold purpose. In the first place it offers to corroborate Theology, in the second to purify it.