These figures are neither hooked nor trident-shaped nor ring-shaped, such figures as these being exposed to collision; but the atoms are impassible, impenetrable; they have indeed figures of their own, which are conceived only by reason.
It is called an atom, by reason not of its smallness but of its indivisibility; in it no vacuity, no passible affection is to be found.
And that there is an atom is perfectly clear; for there are elements which have a perpetual duration, and there are animals which admit of a vacuity, and there is a unity.
Empedocles the Agrigentine, the son of Meton, affirms that there are four elements, fire, air, earth, and water, and two powers which bear the greatest command in nature, concord and discord, of which one is the union, the other the division of beings.

Thus he sings, Hear first the four roots of all created things:-- Bright shining Jove, Juno that beareth life, Pluto beneath the earth, and Nestis who Doth with her tears water the human fount.
By Jupiter he understands fire and ether, by Juno that gives life he means the air, by Pluto the earth, by Nestis and the spring of all mortals (as it were) seed and water.
Socrates the son of Sophroniscus, and Plato son of Ariston, both natives of Athens, entertain the same opinion concerning the universe; for they suppose three principles, God, matter, and the idea.

God is the universal understanding; matter is that which is the first substratum, accommodated for the generation and corruption of beings; the idea is an incorporeal essence, existing in the cogitations and apprehensions of God; for God is the soul and mind of the world.
Aristotle the son of Nichomachus, the Stagirite, constitutes three principles; Entelecheia (which is the same with form), matter, and privation.

He acknowledges four elements, and adds a certain fifth body, which is ethereal and not obnoxious to mutation.
Zeno son of Mnaseas, the native of Citium, avers these to be principles, God and matter, the first of which is the efficient cause, the other the passible and receptive.

Four more elements he likewise confesses..