[10] _Wisdom of God_, 1691. PERIOD III. 1741-1789 Characteristics of the Period. The chief historical events are the decline of the French monarchy, the French revolution, the rise of Prussia, the expansion of England, and the American Declaration of Independence. In the history of thought we remark the introduction of the historical or comparative method, which seeks to co-ordinate facts and to trace events to their causes. Science steadily grows in influence, and freethought wins many triumphs; this is the age of Voltaire, Rousseau, and the Encyclopædists, of David Hume, of the French economists and Adam Smith. Systems of Flowering Plants: Linnæus and the Jussieus. Linnæus is remembered as a man of great industry, enterprise, and sagacity, who was inspired from boyhood by a passion for natural history and spent a long life in advancing it. He was early recognised as a leader in more than one branch of the study. L'Obel, Morison, and Ray had laboured to found a natural system of flowering plants, and it was they who laid the foundation upon which all their successors have built. The work did not, however, go steadily forward on the original plan. When Linnæus entered upon the scene the prevalent systems were only moderately natural, and far from convenient in practice. To place the undescribed species which poured in from North America and other distant countries was a difficult task, with which the universities and botanic gardens of Europe could but imperfectly cope. Linnæus, who had the instincts of a man of business, saw that botany was falling into confusion, and that the only remedy was a quick and easy method, which could be mastered in a few days and applied with certainty. No such method, he well knew, could take into account all the intricate affinities of plants, but to devise a perfect method required the labours of generations of botanists; meanwhile a temporary expedient, full of faults it might be, would remove a pressing evil. Flowering plants had been arranged by the divisions of the ovary, or by the petals and sepals, with no very satisfactory results; it occurred to Linnæus to try the number of the stamens and styles. Any such method was bound to present many anomalies, associating plants which are only distantly related, and separating plants which are closely related; but some of the worst anomalies were avoided and some well-established families (Crucifers, Composites, Labiates) retained at the expense of symmetry. Not even the pressing need of simple definitions, which was allowed to spoil so natural a group as the Umbellifers,[11] could induce Linnæus to place Ranunculus and Potentilla in the same class.