Greek Texts & Translations

Their physical doctrine they divide into sections (1) about bodies; (2) about principles; (3) about elements; (4) about the gods; (5) about bounding surfaces and space whether filled or empty. This is a division into species; but the generic division is into three parts, dealing with (i.) the universe; (ii.) the elements; (iii.) the subject of causation.

The part dealing with the universe admits, they say, of division into two : for with one aspect of it the mathematicians also are concerned, in so far as they treat questions relating to the fixed stars and the planets, e.g. whether the sun is or is not just so large as it appears to be, and the same about the moon, the question of their revolutions, and other inquiries of the same sort. But there is another aspect or field of cosmological ^note inquiry, which belongs to the physicists alone : 7.1.133 this includes such questions as what the substance of the universe is, whether the sun and the stars are made up of form and matter, whether the world has had a beginning in time or not, whether it is animate or inanimate, whether it is destructible or indestructible, whether it is governed by providence, and all the rest. The part concerned with causation, again, is itself subdivided into two. And in one of its aspects medical inquiries have a share in it, in so far as it involves investigation of the ruling principle of the soul and the phenomena of soul, seeds, and the like. Whereas the other part is claimed by the mathematicians also, e.g. how vision is to be explained, what causes the image on the mirror, what is the origin of clouds, thunder, rainbows, halos, comets, and the like.

They hold that there are two principles in the universe, the active principle and the passive. The passive principle, then, is a substance without quality, i.e. matter, whereas the active is the reason inherent in this substance, that is God. For he is everlasting and is the artificer of each several thing throughout the whole extent of matter. This doctrine is laid down by Zeno of Citium in his treatise On Existence, Cleanthes in his work On Atoms, Chrysippus in the first book of his Physics towards the end, Archedemus in his treatise On Elements, and Posidonius in the second book of his Physical Exposition. There is a difference, according to them, between principles and elements ; the former being without generation or destruction, whereas the elements are destroyed when all things are resolved into fire. Moreover, the principles are incorporeal and destitute of form, while the elements have been endowed with form.

Body is defined by Apollodorus in his Physics as that which is extended in three dimensions, length, breadth, and depth. This is also called solid body. But surface is the extremity of a solid body, or that which has length and breadth only without depth. That surface exists not only in our thought but also in reality is maintained by Posidonius in the third book of his Celestial Phenomena. A line is the extremity of a surface or length without breadth, or that which has length alone. A point is the extremity of a line, the smallest possible mark or dot. God is one and the same with Reason, Fate, and Zeus ; he is also called by many other names. 7.1.136 In the beginning he was by himself ; he transformed the whole of substance through air into water, and just as in animal generation the seed has a moist vehicle, so in cosmic moisture God, who is the seminal reason of the universe, remains behind in the moisture as such an agent, adapting matter to himself with a view to the next stage of creation. Thereupon he created first of all the four elements, fire, water, air, earth. They are discussed by Zeno in his treatise On the Whole, by Chrysippus in the first book of his Physics, and by Archedemus in a work On Elements. An element is defined as that from which particular things first come to be at their birth and into which they are finally resolved. 7.1.137 The four elements together constitute unqualified substance or matter. Fire is the hot element, water the moist, air the cold, earth the dry. Not but what the quality of dryness is also found in the air. ^note Fire has the uppermost place ; it is also called aether, and in it the sphere of the fixed stars is first created ; then comes the sphere of the planets, next to that the air, then the water, and lowest of all the earth, which is at the centre of all things.

The term universe or cosmos is used by them in three senses : (1) of God himself, the individual being whose quality is derived from the whole of substance ; he is indestructible and ingenerable, being the artificer of this orderly arrangement, who at stated periods of time absorbs into himself the whole of substance and again creates it from himself.