If we read between the lines of this singular exhibition of force of one kind and weakness of another, it is clear that Descartes believed that he had divined the mode in which the physical universe had been evolved; and the Traité de l’homme and the essay Sur les passions afford abundant additional evidence that he sought for, and thought he had found, an explanation of the phenomena of physical life by deduction from purely physical laws.
Spinoza abounds in the same sense, and is as usual perfectly candid—
“Naturae leges et regulae, secundum quas omnia fiunt et ex unis formis in alias mutantur, sunt ubique et semper eadem.”[31]
Leibnitz’s doctrine of continuity necessarily led him in the same direction; and, of the infinite multitude of monads with which he peopled the world, each is supposed to be the focus of an endless process of evolution and involution. In the Protogaea, xxvi., Leibnitz distinctly suggests the mutability of species—
“Alii mirantur in saxis passim species videri quas vel in orbe cognito, vel saltem in vicinis locis frustra quaeras. Ita Cornua Ammonis, quae ex nautilorum numero habeantur, passim et forma et magnitudine (nam et pedali diametro aliquando reperiuntur) ab omnibus illis naturis discrepare dicunt, quas praebet mare. Sed quis absconditos ejus recessus aut subterraneas abyssos pervestigavit? quam multa nobis animalia antea ignota offert novus orbis? Et credibile est per magnas illas conversiones etiam animalium species plurimum immutatas.”
Thus in the end of the 17th century the seed was sown which has at intervals brought forth recurrent crops of evolutional hypotheses, based, more or less completely, on general reasonings.
Among the earliest of these speculations is that put forward by Benoît de Maillet in his Telliamed, which, though printed in 1735, was not published until twenty-three years later. Considering that this book was written before the time of Haller, or Bonnet, or Linnaeus, or Hutton, it surely deserves more respectful consideration than it usually receives. For De Maillet not only has a definite conception of the plasticity of living things, and of the production of existing species by the modification of their predecessors, but he clearly apprehends the cardinal maxim of modern geological science, that the explanation of the structure of the globe is to be sought in the deductive application to geological phenomena of the principles established inductively by the study of the present course of nature. Somewhat later, P.L.M. de Maupertuis[32] suggested a curious hypothesis as to the causes of variation, which he thinks may be sufficient to account for the origin of all animals from a single pair. Jean Baptiste René Robinet[33] followed out much the same line of thought as De Maillet, but less soberly; and Bonnet’s speculations in the Palingénésie, which appeared in 1769, have already been mentioned. Buffon (1753-1778), at first a partisan of the absolute immutability of species, subsequently appears to have believed that larger or smaller groups of species have been produced by the modification of a primitive stock; but he contributed nothing to the general doctrine of evolution.
Erasmus Darwin (Zoonomia, 1794), though a zealous evolutionist, can hardly be said to have made any real advance on his predecessors; and, notwithstanding the fact that Goethe had the advantage of a wide knowledge of morphological facts, and a true insight into their signification, while he threw all the power of a great poet into the expression of his conceptions, it may be questioned whether he supplied the doctrine of evolution with a firmer scientific basis than it already possessed. Moreover, whatever the value of Goethe’s labours in that field, they were not published before 1820, long after evolutionism had taken a new departure from the works of Treviranus and Lamarck—the first of its advocates who were equipped for their task with the needful large and accurate knowledge of the phenomena of life as a whole. It is remarkable that each of these writers seems to have been led, independently and contemporaneously, to invent the same name of “biology” for the science of the phenomena of life; and thus, following Buffon, to have recognized the essential unity of these phenomena, and their contradistinction from those of inanimate nature. And it is hard to say whether Lamarck or Treviranus has the priority in propounding the main thesis of the doctrine of evolution; for though the first volume of Treviranus’s Biologie appeared only in 1802, he says, in the preface to his later work, the Erscheinungen und Gesetze des organischen Lebens, dated 1831, that he wrote the first volume of the Biologie “nearly five-and-thirty years ago,” or about 1796.
Now, in 1794, there is evidence that Lamarck held doctrines which present a striking contrast to those which are to be found in the Philosophie zoologique, as the following passages show:—
“685. Quoique mon unique objet dans cet article n’ait été que de traiter de la cause physique de l’entretien de la vie des êtres organiques, malgré cela j’ai osé avancer en débutant, que l’existence de ces êtres étonnants n’appartiennent nullement à la nature; que tout ce qu’on peut entendre par le mot nature, ne pouvoit donner la vie, c’est-à-dire, que toutes les qualités de la matière, jointes à toutes les circonstances possibles, et même à l’activité répandue dans l’univers, ne pouvaient point produire un être muni du mouvement organique, capable de reproduire son semblable, et sujet à la mort.