66. Epicurean Physics. -- The physical theory of Epicurus was that everything in Nature is ruled by general natural forces, that there is no such thing as purpose or finality, and that consequently man may lay aside all fear of a Divine interference. He explains the sensible world after the mechanical principles of Democritus (10): that there exist only material, homogeneous atoms, infinite in number. Owing to their weight, these are set in motion in the infinite void of space. There is, however, this difference between the two systems. In that of Democritus, the atoms interfere with each other in their fall, thus producing eddying motions; while in that of Epicurus, all fall with the same speed Perpendicularly and without touching each other through the void which can offer them no resistance. Epicurus, however, influenced by moral considerations, attributes to the atoms a discretionary power of declination (the clinamen of Lucretius) by which they can deviate a little from the perpendicular. It is the natural play of these atomic movements, independent of gravity, that produces the shocks and eddies in them.

The accumulation of atoms, under the action of gravity, produces worlds separated from one another by vacant spaces. The different shapes of the atoms explain the appearance of the different elements, -- especially of the earth, from which are generated plants, animals, and man.