 In keeping with these ideas, Bruno populated the principal bodies with life-forms of every kind. Each region of each principal body comprised matter which, circumstances permitting, became a plant or animal, even a rational animal. This last category included human beings and also demons, in other words, rational beings with rarefied bodies made of pure aether or combinations of aether with air, water or earth. The latter, to judge by the demons frequenting the elemental regions of our globe, were generally, but by no means invariably, more intelligent than human beings. Within the mountains were dim-witted troglodytes jealously guarding the earth’s mineral veins (BOL I.2, 61, 282; III, 431). Long-living but of feeble intelligence, they had little commerce with human beings. Stone-throwing demons, another species of earthy demon, of the kind described by the Byzantine author Michael Psellos, had lairs in the vicinity of Nola and habitually pelted those who passed nearby at night, as Bruno knew from personal experience (BOL III, 431). Nymphs with predominantly aqueous bodies lived secluded in grottos (BOL I.2, 282; III, 181). The variety of demonic life was such that it “far surpassed that of sensible things” (BOL III, 427, 429). A comparable diversity was evident among human beings, who differed in skin colour and stature from region to region (BOL I.2, 282, 284). The variations reflected their diverse habitats. When extinguished by a cataclysm of some kind, they regenerated spontaneously (BOL I.2, 282), in the manner that Avicenna and, if only as a philosophical possibility, some Christian authors had described. The novelty in Bruno’s interpretation was the idea that spontaneous generation explained the variety of life in an infinite and infinitely varied universe rather than the survival of a privileged species on this earth.