Others have resisted the impulse of the time; they have remained faithful to method, the mother of modern science; they have carefully preserved their inheritance of solid and precise knowledge, acquired from past centuries. They cannot on that account be accused of acting from routine or be considered as retrograding. As warmly as the most ardent partisans of the so-called advanced theories, they have applauded all the progress, and have received with equal favour new ideas, on the condition of exposing them to experiment and observation. But when they meet with questions the solution of which is at present impossible, and will perhaps always be so, they have not hesitated to answer:—WE DO NOT KNOW;—and when they find purely metaphysical theories are being imposed upon them, they have protested in the name of experiment and observation. I venture to say that I have always remained faithful to the ranks of this phalanx, to which the future distinctly belongs. For this reason, to those who question me upon the problem of our origin, I do not hesitate to answer in the name of science:—I DO NOT KNOW. I do not on that account anathematise those who consider they ought to act otherwise, nor do I greatly blame their boldness. The study of second causes has enabled man to explain scientifically the present constitution of the inorganic world; and it is quite legitimate to attempt to account for the present state of the organic world by causes of the same nature; perhaps success will one day crown our efforts, and should they for ever remain unrewarded, as they have hitherto done, they will still possess a certain utility. These efforts of the imagination provoke new research, make new openings, and thus render a service to real science in the world of facts, as well as in that of ideas. If Darwin had not been actuated by his preconceptions, he would probably never have accomplished his excellent work upon the 150 races of pigeons, nor developed his theory of the struggle for existence and natural selection, which accounts for so many facts. Unfortunately, from having forgotten the works of their predecessors, Darwin and his followers have drawn erroneous conclusions from these premises. They imagine they have given explanations when they have given none. This is what I have endeavoured to show. I have been obliged to resume the debate; it is for the impartial and unprejudiced reader to decide between us. BOOK III. ANTIQUITY OF THE HUMAN SPECIES. CHAPTER XII. AGE OF THE HUMAN SPECIES.—PRESENT GEOLOGICAL EPOCH. I. Without prejudging the future, we have been obliged to acknowledge that the problem of the specific origin of man cannot be solved, or even attempted, with the scientific data which we at present possess. This is not quite so much the case with certain questions which are naturally suggested to the mind by the preceding.