Tycho Brahe’s observations in the laws which bear his name. He afterwards demonstrated the quantitative ratios on the basis of the facts of experience. Here his method involved the combination of the experimental with the mathematical method. Just as he had at first established the principle that nature conforms to mathematical laws by the theological method, so he further believes that the planets are guided in their course by separate planetary souls, even as the entire world-system is directed by the world-soul which dwells in the sun. His explanation of nature therefore was thoroughly animistic or mythological. Later on in life he held that science must make no assumptions except such as can be actually deduced from experience. He calls such causes vera causa. He also rejected the idea of planetary souls which as a matter of fact are never actually given in experience. In his Astronomia nova s. physica coelestis (1609) he makes the transition from theology and animism to pure natural science. He defends his belief in the importance and truth of the quantitative method psychologically and empirically as well as theologically. Mathematical knowledge is the clearest and the most certain knowledge which we possess and it becomes us therefore to apply it as widely as possible. The processes of nature are qualitatively modified by our subjective states (pro habitudine subjecti). Perfect certainty and objectivity can only be attained by the quantitative method. And, finally, experience reveals the fact that all material phenomena have quantitative, especially geometrical, attributes; “the method of measurement can be applied wherever there is matter” (ubi materia, ibi geometria). As a matter of fact the universe participates in quantity (mundus participat quantitate).
Kepler elaborates his general conception of scientific
