the same occasions of observation; it is thus that psychology, based upon simple reflection, has not farther progressed in our days than at Athens or at Alexandria; from Plato to Descartes there is only the distance between one system and the other. “Historians of that which is,” has said the illustrious chief of the philosophical school of France, Etienne Geoffroy Saint-Hilaire, “we cannot fail, except when we cease to relate the truth.”[7] Now, truth in science cannot be governed except by two means, reasoning after the manner of mathematics, and observation, of which experiment is but a variety. Every idea _à priori_, every hypothesis is only good if we accept it with a strong determination of abandoning it if the facts are no longer explicable by its means. Without this, its influence is disastrous, let the origin of this previous idea be in ourselves or in others, whether it is our own or has been imposed upon us.[8] In starting with a preconceived idea one arrives most often, in science, at false allegations, always at uncertainties. It is upon reasons of this sort that some have not feared to rest the theory of the unity of the human race;[9] since this hypothesis being accepted, they have caused, willingly or otherwise, their observed facts to correspond with it. Were the generally-admitted principles of classification irksome to them? They passed on; they shut their eyes to the most profound, the most positive, the most evident differences. Ought not, then, unity to triumph? What did it signify, besides, whether the Negro descended from the white man, or the contrary--for these two opinions have been defended; for some, a few generations have been sufficient to transform the fine Greek blood, which gave models to Phidias and Praxiteles, into an Australian aboriginal. For others, the Negroes were the true representation of our first parents, that perfect work which last of all left the hands of God. Lieut.-Colonel H. Smith[10] would admit that in the beginning were created separately certain groups of men, if revelation were not positive on this point. We notice especially in Kaempfer a specimen of what we may call _orthodox ethnology_, which is curious above all things; having discovered that the Japanese have nothing in common with the Chinese, he decides, with a marvellous assurance, that they are directly descended from the men on the scaffoldings of the Tower of Babel. And as their language resembles no other tongue, he draws the conclusion that their ancestors must have travelled very fast, so as not to have become acquainted with anybody else![11]