A well constructed synthesis must necessarily precede every theory of nature. Descartes, when working out his system of whirlwinds, formulated a conception which was certainly very inexact; but the facts upon which this theory rested were so well selected, they responded so exactly to the requirements of science, that when Newton came, with his _system of attraction_, it only remained to apply the new hypothesis to the facts collected by Descartes for his _whirlwinds_, and there was real astronomy, the true physics. When Linnæus created his _system of botany_, he made an undeniably artificial distribution of the vegetables, and Linnæus himself perfectly understood the defects of his system. But, owing to this artificial method, he succeeded in grouping all the plants into a methodical catalogue. If the principle of classification was bad, the service rendered to botany by this catalogue was immense. It was not, in fact, until after Linnæus' time that the immense mass of facts which he collected could be put in order, and the study of the vegetable world made to progress from those data. Botany dates from the publication of the _systema naturæ_ of the immortal botanist of Upsal. We do not pretend to put forward an irreproachable theory of the universe in this work, but simply to collect together and methodically group the facts upon which such a theory ought to rest, facts physical, metaphysical, and moral. FOOTNOTES: [18] "_La Pluralité des existences de l'âme_," Paris, p. 450. [19] "_La Religion des Hindous selon les Védas_," par Lanjuinais, Paris, p. 286. [20] "_La Religion des Hindous selon les Védas_," pp. 324, 325. [21] "_Histoires_," Vol. II. ch. cxxiii. (translated by M. Larcher.) [Illustration] CHAPTER THE NINETEENTH. SEQUEL TO OBJECTIONS.--IT IS INCOMPREHENSIBLE HOW THE RAYS OF THE SUN, BEING MATERIAL SUBSTANCES, CAN BE THE GERMS OF SOULS, WHICH ARE IMMATERIAL SUBSTANCES. OUR system of nature may be met with the following final objection. It will be said, how can the rays of the sun, being material bodies, convey animated germs which are immaterial substances? These terms exclude each other. We find, in the Scriptures, a magnificent comparison, of which we shall avail ourselves in order to answer this objection, or rather, this question. Saint Matthew speaks of a grain of mustard seed, that is to say, of a tree germ, which, cast into the earth, produces a herbaceous plant, then a tree with majestic branches, and he is astonished to behold the imposing lord of the forests, which, laden with flowers and fruit, towers aloft in majestic beauty, and gives shelter under its shadow to the weary birds, springing from a humble little seed. Not only, says the evangelist, is there no resemblance between the tree and its original seed, but there does not exist in the tree a single atom of the matter of which the seed was primarily composed.