  The celestial or, as Bruno called them, “principal” bodies glided weightlessly within an infinite “receptacle” or “expanse” of aether (BOI II, 110) like specks of dust in the sunlit air (BOL I.1, 262; I.2, 91). What made them move? Their souls. They were animate and, as their orderly patterns of motion attested, intelligent too. Aristotle had suggested this among other possible explanations for celestial motion. Most patristic and scholastic authors, anxious to discourage polytheism, had rejected the idea. Ficino’s revival of Platonism, however, had given a new lease of life to the idea that the celestial bodies were animate. True to form, Bruno, though indebted to Ficino on this as on many other scores, quoted the Book of Job (28:20–21) as his authority. In each solar system or, in Bruno’s terminology, “synod” the suns and earth regulated their motions autonomously to their mutual advantage. From the earths, the suns absorbed vaporous exhalations. In exchange the sun produced the light and heat that the earths, as “animals”, needed in order to host living things. No part of them remained forever barren thanks to the several approximately circular revolutions that they performed. Nature, for Bruno no less than for Aristotle, did nothing in vain (BOL III, 108).