Third, and highest, we reach the Spiritual Kingdom, or the Kingdom of Heaven. What its characteristics are, relatively to any hypothetical higher Kingdom, necessarily remain unknown. That the Spiritual, in turn, may be the preparation for, and the prophecy of, something still higher is not impossible. But the very conception of a Fourth Kingdom transcends us, and if it exists, the Spiritual organism, by the analogy, must remain at present wholly dead to it. The warrant for adding this Third Kingdom consists, as just stated, in the fact that there are organisms which from their peculiar origin, nature, and destiny cannot be fitly entered in either of the two Kingdoms now known to science. The Second Kingdom is proclaimed by the advent upon the stage of the First, of _once-born_ organisms. The Third is ushered in by the appearance, among these once-born organisms, of forms of life which have been born again--_twice-born_ organisms. The classification, therefore, is based, from the scientific side on certain facts of embryology and on the Law of Biogenesis; and from the theological side on certain facts of experience and on the doctrine of Regeneration. To those who hold either to Biogenesis or to Regeneration, there is no escape from a Third Kingdom.[98] There is in this conception of a high and spiritual organism rising out of the highest point of the Organic Kingdom, in the hypothesis of the Spiritual Kingdom itself, a Third Kingdom following the Second in sequence as orderly as the Second follows the First, a Kingdom utilizing the materials of both the Kingdoms beneath it, continuing their laws, and, above all, accounting for these lower Kingdoms in a legitimate way and complementing them in the only known way--there is in all this a suggestion of the greatest of modern scientific doctrines, the Evolution hypothesis, too impressive to pass unnoticed. The strength of the doctrine of Evolution, at least in its broader outlines, is now such that its verdict on any biological question is a consideration of moment. And if any further defence is needed for the idea of a Third Kingdom it may be found in the singular harmony of the whole conception with this great modern truth. It might even be asked whether a complete and consistent theory of Evolution does not really demand such a conception? Why should Evolution stop with the Organic? It is surely obvious that the complement of Evolution is Advolution, and the inquiry, Whence has all this system of things come, is, after all, of minor importance compared with the question, Whither does all this tend? Science, as such, may have little to say on such a question. And it is perhaps impossible, with such faculties as we now possess, to imagine an Evolution with a future as great as its past. So stupendous is the development from the atom to the man that no point can be fixed in the future as distant from what man is now as he is from the atom. But it