 Copernicus was inspired by these testimonia about Hicetas and Ecphantus, as well as those about Philolaus, to consider the motion of the earth (see below, sect. 5.2). Ecphantus developed his own original form of atomism. He is best understood as reacting to and developing the views of Democritus. He agreed with Democritus 1) “that human beings do not grasp true knowledge of the things that are, but define them as they believe them to be” (DK I 442.7–8; cf. Democritus Frs. 6–10) and 2) that all sensible things arise from indivisible first bodies and void. He differs from Democritus, however, in supposing that atoms are limited rather than unlimited in number and that there is just one cosmos rather than many. As in Democritus, atoms differ in shape and size, but Ecphantus adds power (dynamis) as a third distinguishing factor. He explains atomic motion not just in terms of weight and external blows, as the atomists did, but also by a divine power, which he called mind or soul, so that “the cosmos was composed of atoms but organized by providence” (DK I 442.21–22). It is because of this divine power that the cosmos is spherical in shape. This unique spherical cosmos is reminiscent of Plato’s Timaeus, but the rest of Ecphantus’ system differs enough from Plato that there is no question of its being a forgery based on the Timaeus. One testimony says that he was the first to make Pythagorean monads corporeal, thus differing from the fifth-century Pythagoreans described by Aristotle, who do not seem to have addressed the question of whether numbers were physical entities or not.