Ancient Greek philosophers like Thales, Anaxagoras (ca. 500 BC – 428 BC), Epicurus and Democritus prefigure later materialists. The Latin poem De Rerum Natura by Lucretius (ca. 99 BC – ca. 55 BC) reflects the mechanistic philosophy of Democritus and Epicurus. According to this view, all that exists is matter and void, and all phenomena result from different motions and conglomerations of base material particles called "atoms" (literally: "indivisibles"). De Rerum Natura provides mechanistic explanations for phenomena such as erosion, evaporation, wind, and sound. Famous principles like "nothing can touch body but body" first appeared in the works of Lucretius. Democritus and Epicurus however did not hold to a monist ontology since they held to the ontological separation of matter and space i.e. space being "another kind" of being, indicating that the definition of "materialism" is wider than given scope for in this article.

De Rerum Natura is a poem by who?