Having thus brought together the whole of the available evidence bearing upon the questions treated in this volume, I claim that certain definite conclusions have been reached and proved, and that certain other conclusions have enormous probabilities in their favour. The conclusions reached by modern astronomers are: (1) That the stellar universe forms one connected whole; and, though of enormous extent, is yet finite, and its extent determinable. (2) That the solar system is situated in the plane of the Milky Way, and not far removed from the centre of that plane. The earth is therefore nearly in the centre of the stellar universe. (3) That this universe consists throughout of the same kinds of matter, and is subjected to the same physical and chemical laws. The conclusions which I claim to have shown to have enormous probabilities in their favour are-- (4) That no other planet in the solar system than our earth is inhabited or habitable. (5) That the probabilities are almost as great against any other sun possessing inhabited planets. (6) That the nearly central position of our sun is probably a permanent one, and has been specially favourable, perhaps absolutely essential, to life-development on the earth. * * * * * These latter conclusions depend upon the combination of a large number of special conditions, each of which must be in definite relation to many of the others, and must all have persisted simultaneously during enormous periods of time. The weight to be given to this kind of reasoning depends upon a full and fair consideration of the _whole_ evidence as I have endeavoured to present it in the last seven chapters of this book. To this evidence I appeal. * * * * * This completes my work as a connected argument, founded wholly on the facts and principles accumulated by modern science; and it leads, if my facts are substantially correct and my reasoning sound, to one great and definite conclusion--that man, the culmination of conscious organic life, has been developed here only in the whole vast material universe we see around us. I claim that this is the logical outcome of the evidence, if we consider and weigh this evidence without any prepossessions whatever. I maintain that it is a question as to which we have no right to form _a priori_ opinions not founded upon evidence. And evidence opposed to this conclusion, or even as to its improbability, we have absolutely none whatever.