However, Gilbert's efforts towards a magnetic philosophy did find approval in two of the men that made the seventeenth century scientific revolution. While Galileo Galilei[210] was critical of Gilbert's arguments as being unnecessarily loose, he nevertheless saw in them some support for the Copernican world-system. Johannes Kepler[211] found in Gilbert's explanation of the loadstone-earth a possible physical framework for his own investigations on planetary motions. [210] Galileo Galilei, _Dialogue on the great world systems_, in the translation of T. Salusbury, edited and corrected by G. de Santillana, University of Chicago Press, 1953, pp. 409-423. [211] Cassirer, _op. cit._ (footnote 3), vol. 1, p. 359-367. Yet Galileo and Kepler had moved beyond Gilbert's world of intellectual experience. They were no longer concerned with determining the nature of material things in order to explain their qualities. Instead, they had passed into the realm of the mathematical relations of kinematics: quantitative law had replaced qualitative experience of cause and effect. Gilbert had some intimations of the former, but he was primarily concerned with explaining magnetism in terms of substance and attribute. He had to ascertain the nature of the loadstone and of the earth in order to explain their properties and their motions. He even went further and explained the nature of the form of the loadstone. His method of determining the nature of a substance was a rather primitive one--it was not by a process of induction and deduction, nor by synthesis and analysis, nor by "resolutio" and "compositio," but by the use of analogies. He compared the natural history of metals and rocks with that of plants, and gave the two former the same kind of principle as the last. He determined the nature of the entity behind electric attraction by finding that such attractions could be screened, and hence it had to be corporeal. After comparing this "corporeal" attraction with that of the surface forces of a fluid, he concluded that the entity was a subtle fluid. He determined the nature of the entity behind magnetic coition by (incorrectly) finding that it cannot be screened, and hence the cause had to be a formal one. Since both stars and the loadstone can carry out regular motions, and stars had souls, the form of the loadstone had to be a soul. The method of analogy was used again in his comparison of the properties of a magnetized needle placed over a terrella with the properties of a compass placed over the earth, whence he concluded the earth to be a giant loadstone. Since the earth resembled the other celestial globes, it had to have, the circular inertia of these globes.[212] As for his magnetic experiments to show physically that the earth moved, and his unbridled speculations on the "animae" of the celestial globes, one is inclined to agree with Bacon's estimate of his magnetic philosophy.