  Telesio's vision of the genesis of nature is simple to the point of being archaic, yet at the same time astonishingly modern in the sense that he seems to have been one of the very first defenders of a theory of natural evolution without metaphysical or theological presuppositions. According to his De rerum natura, the only things which must be presupposed are passive matter and active force, the latter of which Telesio thought of as twofold, heat and cold. These principles were meant to replace the Aristotelian metaphysical principles of matter and form. In order to explain how all natural beings came into existence by  these opposing forces, Telesio presumed that in the beginning God had created two primary globes, the sun and the earth, the sun being the seat of heat, the earth that of coldness, and that He had separated them with such a distance in space that they could not extinguish each other (DRN book I, ch. IV). All natural things result from the battle of these antagonistic forces for the possession of matter. The main region of that creative battle is the surface of the earth, where they create metals, stones and animate beings. The primary activity of warmth is to move fast and to dilate and rarefy matter, whereas that of cold is to hinder movement and to condense matter. Things differ according to the amount of heat or cold they possess (and therefore according to their density and derivative qualities such as velocity and colour). The quantity of matter is not changed through the action of these forces upon it. The role of heat, cold and matter as ‘natural principles’ had been highlighted before by Girolamo Fracastoro in the first version of the Homocentrica and in the dialogue Fracastorius sive De anima (Lerner 1992), as well as by Girolamo Cardano in his Liber unicus de natura.