Let us observe here that the progressive order which we have indicated for the migration of soul through the bodies of different animals, is precisely that which nature followed in the first creation of the organized beings which people our globe. It will be seen in ch. xiv., pp. 196-200, that plants zoophytes, mollusca, and articulated animals are the first living beings which appeared on our globe. After them came the fishes, and then the reptiles. After the reptiles birds, and at a later period mammifers appeared. Thus our system responds to the routine which nature has followed in the creation of plants and animals. Such is the system which we have conceived as explanatory of the part assigned to animals on our globe. The basis of this system, as will be seen, is the intelligence accorded to animals. We entirely repel the generally held opinion, that beasts do not possess intelligence, and that it is replaced by an obscure faculty which is called instinct. But this theory gives no reason, it merely puts a word in the place of an explanation. By a simple phrase people imagine they resolve one of the great problems of nature. The timid and conventional philosophy of our time has hitherto accommodated itself to this method of eluding great difficulties, but the moment now appears to have come for a deeper study of the problems of nature, and for no longer remaining content with the substitution of words for things. There was no hesitation in ancient times about according intelligence to animals. Aristotle and Plato expressed themselves quite clearly on this point: they admitted no doubt of the reasoning powers of beasts. The most celebrated modern philosophers, Leibnitz, Locke, and Montaigne; the most eminent naturalists, Charles Bonnet, Georges Leroy, Dupont de Nemours, Swammerdam, Réaumur, &c., granted intelligence to animals. Charles Bonnet understood the language of many animals, and Dupont de Nemours has given us a translation of the "_Chansons du Rossignol_" and the "_Dictionnaire de la Langue des Corbeaux_." It is, therefore, difficult to understand how a contrary thesis became prevalent in this age, how Descartes and Buffon, the declared adversaries of animal intelligence, have succeeded in turning the scale in favour of their ideas. Descartes regarded animals purely as machines, as automata provided with mechanical apparatus. It would be difficult to surpass our great philosopher in absurdity when he treats of these animal machines.[12] _Equidem bonus dormitat Descartes._ The systematic errors of Buffon on the same subject are well known.