We may state that the ideas here developed—very imperfectly of course, as must always be the case in matters of the kind—are not the result of hasty guessing, but have been pressed on us by the reflections and discussions of several years. We have to thank many of our friends, theological as well as scientific, for ready and valuable assistance. The matter of our work has certainly gained by this, though it is likely that the manner may have suffered by the introduction, here and there, of peculiarities of style which could not easily be removed without damage to the sense. PREFACE TO THE SECOND EDITION. As a preface to our Second Edition, we cannot do better than record the experience derived from our first. It is indeed gratifying to find a wonderful want of unanimity among the critics who assail us, and it is probably owing to this cause that we have been able to preserve a kind of kinetic stability, just as a man does in consequence of being equally belaboured on all sides by the myriad petty impacts of little particles of air. Some call us infidels, while others represent us as very much too orthodoxly credulous; some call us pantheists, some materialists, others spiritualists. As we cannot belong at once to _all_ these varied categories, the presumption is that we belong to none of them. This, by the way, is our own opinion. Venturing to classify our critics, we would divide them into three groups:— (1.) There are those who have doubtless faith in revelation; but more especially, sometimes solely, in _their own_ method of interpreting it; none, however, in the method according to which really scientific men with a wonderful unanimity have been led to interpret the works of nature. These critics call us, some infidels, some pantheists, some dangerously subtle materialists, etc. (2.) There are those who have faith in the methods according to which men of science interpret the laws of nature, but none whatever in revelation or theology. These consider us as orthodoxly credulous and superstitious, or as writers of ‘the most hardened and impenitent nonsense that ever called itself original speculation.’ (3.) There are those who have a profound belief that the true principles of science will be found in accordance with revelation, and who welcome any work whose object is to endeavour to reconcile these two fields of thought. Such men believe that the Author of revelation is likewise the Author of nature, and that these works of His will ultimately be found to be in perfect accord. Such of this school as have yet spoken have approved of our work. Our readers may judge for themselves which of these three classes of belief represents most nearly the true Catholic Faith.