The Systematic Period Atomism, Plato and Aristotle. The Peripatetic School: Strato and Theophrastus
IN the writers discussed hitherto the distinction between the bodily and the mental becomes gradually more explicit as we pass from the earliest hylozoistic systems, where the material and the living are indistinguishably merged, to the systems of Empedocles and Anaxagoras, in which physical and non-physical principles begin to be separated as two fundamentally different categories, both, however, being recognized as true explanatory principles. In the system of Leucippus and Democritus philosophy enters upon a critical and controversial phase; the dualism heretofore merely implicit comes to conscious recognition, and is subjected to a methodical criticism. The dualistic interpretation is meanwhile continued and greatly elaborated in the systems of Plato and Aristotle, in whom a world-view wholly different from the materialistic atomism of Democritus, a worldview destined to mould subsequent philosophy in an unprecedented manner, begins to take definite shape.
Leucippus, of doubtful date and antecedents, and Democritus of Abdera in Thrace (c. 460-370), recognize only two principles of things, the "full" and the "void," being and non-being (ὂν and μὴ ὂν). The