by the aid of mathematics. Mathematical deduction is the only method of discovering the unknown from the given facts of nature. We thus find even here a clear expression of all the characteristics of modern method, viz. the proper coordination of induction and deduction.—Certain statements of Leonardo’s indicate a sturdy naturalism. The only thing we can know about the soul is the nature of its functions and its activity as an organic principle; whoever cares to know more must inquire of the Monks! Nature consists of a majestic cycle between the inorganic and the organic, and between the animate and the inanimate. Nature always takes the simplest course. There is reason therefore to hope for a great future with respect to the knowledge of nature.—Leonardo suggested a number of interesting anticipations of the principle of inertia and of energy. He stands solitary and alone in his own age. It was not until a century later that any advancements were made along the lines which he indicated.
b. John Kepler (1571-1630), the famous astronomer, is an interesting example of the evolution of an exact scientific conception of nature from a mystic-contemplative starting-point. His first treatise (Mysterium cosmographicum, 1597) is based on theological and Pythagorean principles. The universe is the manifestation of God. The paths and motions of the heavenly bodies must therefore reveal certain harmonious and simple geometrical relations. The Holy Ghost is revealed in the harmonious ratio of magnitudes of stellar phenomena, and Kepler thinks it possible to construe this magnitudinal ratio. Later on however he simply maintained the general belief that certain quantitative ratios must exist between the motions of the planets and formulated the results deduced from