CARDANO ATTEMPTS to conceive of the world as a unified whole. In accordance with the idea of unity of the terrestrial and the celestial, of the physical and the spiritual world he believes in a single vital principle: the “World-soul.” At the same time he is greatly impressed by the profusion of phenomena that he perceives in the world and that he wishes to include in his extensive knowledge. It seems to him that a single principle cannot account for the wealth of diverse forms of which he is continually aware. Instead, many principles must exist. Clearly, the old dialectic of “the one and the many” is very much part of his thinking. Anyone studying Cardano’s philosophy of nature ought to read De Natura first, as Cardano himself advises in the list of his works, De libris propriis. Closely related to De Natura is De Uno. Both works were probably written around 1560, but De Natura was not printed until the publication of Spon’s edition of the Opera.