a system of physics which accounts for the various phenomena of nature by the physical properties and arrangement of the corpuscles or atoms supposed to be the constituent materials of all natural bodies; such as their motion, figure, rest, position, attraction, or repulsion. This system is of great antiquity. It was taught in Greece by Leucippus and Democritus; and the noble poem of Lucretius, De Rerum Natura, is devoted to its explanation. It is otherwise called the Atomic Philosophy. This ancient system, divested by Newton and others of numerous absurdities, has now become the basis of mechanical and experimental philosophy. (See the article Epicurean Philosophy.)