  Commendable though his achievement had been, Copernicus had remained unaware of the full implications of his heliocentric hypothesis. It was left to Bruno, the philosopher, to accomplish the full revolution of thought, pass beyond the quantitative sensible realm that, important stepping stone though it was, had unduly preoccupied mathematicians like Copernicus and proceed to knowledge of what could be discerned by reason alone (BOI I, 448–454). Copernicus’s most egregious shortcoming in this respect was his failure to recognize that his heliocentric hypothesis disproved Aristotelian and scholastic arguments that the cosmos, or rather universe, was finite and unique. If the heavens were infinite, these arguments ran, then their outermost regions would —impossibly— revolve infinitely fast around the earth at centre of the cosmos. Nor could there be more than one cosmos, because, if there were, then a displaced particle of an element would —no less impossibly—have two or more natural places to which it should return. These objections carried no weight in a heliocentric world. The apparent daily rotation of a firmament or “sphere of fixed stars” around the earth was an illusion created by the earth’s rotation around its axis as it circled the sun. The universe was not, Bruno insisted, a finite globe composed of concentric spheres, “like an onion” (BOL I.2, 261), to use a common simile. Instead it was an infinite, homogeneous expanse populated by an infinite number of solar systems like our own. How far his achievement surpassed that of Columbus, who had discovered just one continent on one earth (BOI I, 451–452)! Lucretius, Nicholas of Cusa (1401–64) and counterfactual scholastic discussions concerning the plurality of worlds are evident influences. The authority that Bruno particularly liked to invoke, however, was Scripture. The infinite number of celestial bodies corresponded to “those so many hundreds of thousands [of angels]”—an allusion to Daniel 7:10—“that assist in the ministry and contemplation of the first, universal, infinite and eternal efficient cause” (BOI I, 455).