IV. Anyone who refuses to accept these conclusions must either deny all the facts of which it is the necessary consequence, or reject the method employed in the examination and appreciation of these facts. But these facts are borrowed entirely either from scientific experiments, made without any discussion or controversy by men of the highest authority, or drawn from the innumerable experiments which are daily practised by agriculturalists, horticulturists, and breeders. It is therefore very difficult to deny them. As to the method, it is evident that it rests entirely upon the identity of the general laws governing all organised and living beings. Few true men of science will, I am sure, refuse to admit such a starting point as this. Now I wish that candid men, who are free from party-spirit or prejudices, would follow me in this view, and study for themselves all these facts, a few of which I have only touched upon, and I am perfectly convinced that they will, with the great men of whom I am only the disciple,—with Linnæus, Buffon, Lamarck, Cuvier, Geoffroy, Humboldt and Müller, arrive at the conclusion that _all men belong to the same species_, and that there is but _one species of man_. BOOK II. ORIGIN OF THE HUMAN SPECIES. CHAPTER X. ORIGIN OF SPECIES.—HYPOTHESES OF TRANSMUTATION.—DARWINISM. I. The unity of the human race raises some general questions, and entails consequences which we must now examine. The first question which is suggested to the mind is evidently that of _origin_. Without abandoning the strictly scientific aspect of the subject, that is to say, confining ourselves to the results of experiment and observation, can we explain the appearance on our globe of a being which forms a kingdom by itself? I do not hesitate to reply in the negative. Let us admit at starting that we cannot consider separately the question of the human origin. Whatever may be the cause or causes which preside over the birth or the development of the organic kingdom, it is to them that the origin of all organised and living bodies must be traced. The similarity between all the essential phenomena which they exhibit, the identity of the general laws which govern them, render it impossible to suppose that it can be otherwise. The problem then of the origin of mankind becomes identical with that of all animal and vegetable species.