Lives and Opinions of Eminent Philosophers

​They say that the substance of all existing things is primary matter, as Chrysippus states in the first book of the Physics and also Zeno. Matter is that from which anything whatever is produced. It is called by two names, substance and matter, both that of all things and that of the parts. The matter of all things, then, neither increases nor diminishes, but that of the parts both increases and diminishes. Substance, according to them, is body and is finite, as Antipater says in the second book of On Substance and Apollodorus in the Physics. It is also passive, as the same author says; for if it were immutable, the things produced from it would not have been produced. From this also follows that division is ad infinitum (which Chrysippus calls without limit, but not ad infinitum; for there is no infinite thing into which the division occurs, but rather the division is unending).

​And blendings, as Chrysippus says in the third book of the Physics, occur through and through, and not by circumscription and juxtaposition; for a little wine thrown into the sea will co-extend with it for a certain extent, and then be destroyed together with it. They also say that there are certain spirits that have sympathy with men, being overseers of human affairs; and that heroes are the surviving souls of the virtuous. Among the phenomena occurring in the air, they say that winter is the air above the earth cooled by the sun's departure into the distance, and spring is the temperate blend of the

​air during its course toward us, summer is the air above the earth heated by the sun's course toward the north, and autumn occurs by the sun's retreat away from us. Winds are currents of air, and their varying appellations arise from the places from which they blow. The cause of their generation is the sun vaporizing the clouds. The rainbow is rays reflected from moist clouds or, as Posidonius says in the Meteorology, the reflection of a segment of the sun or moon in a dewy cloud that is concave and continuous to appearance, appearing as if in a mirror along the circumference of a circle. Comets, bearded stars, and torch-stars are fires subsisting when dense air is carried up into the ethereal region.

​A flash (meteor) is the kindling of concentrated fire borne rapidly through the air and exhibiting an appearance of length. Rain is the transformation from cloud into water, whenever moisture carried up from either earth or sea is not fully processed by the sun; and this, when cooled, is called frost. Hail is a frozen cloud shattered by wind; and snow is moisture from a frozen cloud, as Posidonius says in the eighth book of the Physical Discourse. Lightning is the kindling of clouds rubbing against one another or torn apart by wind, as Zeno says in On the Whole; thunder is their sound resulting from rubbing or bursting;

​and a thunderbolt is a violent kindling falling upon the earth with great force when clouds rub against one another or are torn apart by wind; others define it as a whirlwind of fiery air violently borne downward. A typhoon is a vast, violent, and wind-driven thunderbolt, or a smoky blast of a ruptured cloud; a fiery whirlwind is a cloud torn open all around by fire accompanied by wind. Earthquakes occur when a blast flows into the hollows of the earth or is confined within the earth, as Posidonius says in the eighth book; and of these, some are shakers, some fissures, some tilters, and some upheawers.