 The principal bodies, human beings and demons were the three genera of rational animal inhabiting the universe. In one important respect, however, principal bodies were unique. Like accomplished musicians—here Bruno adapted an analogy used by Plotinus and many others to illustrate how nature operated non-discursively according to a final cause—they did not think rationally, proceeding from one thought to the next as they executed their roles. Their intellects dominated their animal bodies, enabling them to move intuitively in accordance with the ends proper to them. Unlike human beings, too, the celestial “animals” were eternal and hence did not reproduce, grow or decay. Though corruptible intrinsically, they were, as the Chaldeans and Plato had taught, sustained by divine providence (for providence, see   Section 5).  This is, at least, what Bruno tended to think even if he conceded, uncharacteristically, that he was uncertain on this point (Granada, 2000). In all other respects, the principal bodies were animals like any other. Stones and other parts of our earth, for example, might seem inanimate but, as parts of a principle body, they were, like the bones, nails and hair of an animal, alive, if only vestigially. Like animals, too, the principal bodies fed and excreted. They expelled stray particles from the surrounding aether and in compensation emitted others, an idea inspired by Lucretius’s concept of simulacra (On the Nature of Things, IV.54–268).