Lives and Opinions of Eminent Philosophers

​The cosmos is one and finite, having a spherical shape; for such a shape is most suitable for motion, as Posidonius says in the fifth book of the Physical Discourse and the school of Antipater in their works On the Cosmos. Surrounding it from the outside is an infinite void, which is incorporeal; and the incorporeal is that which is capable of being occupied by bodies, but is not occupied. But within the cosmos there is no void, but it is unified; for the sympathy and tension of celestial things with terrestrial things necessitates this. Chrysippus speaks about the void in On the Void and in the first book of Physical Arts, and Apollophanes in the Physics, and Apollodorus, and Posidonius in the second book of the Physical Discourse. And these things too are likewise incorporeals.

​Furthermore, time also is incorporeal, being the interval of the motion of the cosmos. Of this, the past and the future are infinite, but the present is finite. They also hold that the cosmos is perishable, inasmuch as it is generated according to the principle of things conceived through perception: that of which the parts are perishable is itself perishable as a whole; and the parts of the cosmos are perishable, for they transform into one another; therefore the cosmos is perishable. And if anything is susceptible to change for the worse, it is perishable; therefore the cosmos is too, for it dries up and turns to water.

​The cosmos comes to be when substance is turned from fire through air into moisture, then the coarse part of it is compacted and completed as earth, while the fine part is vaporized, and this, being thinned still further, engenders fire; then, by mixture from these, plants and animals and the other kinds. Now concerning the generation and destruction of the cosmos, Zeno speaks in On the Whole, Chrysippus in the first book of the Physics, Posidonius in the first book of On the Cosmos, Cleanthes, and Antipater in the tenth book of On the Cosmos. Panaetius, however, declared the cosmos to be imperishable. That the cosmos is also an animal, rational, animate, and intelligent is stated by Chrysippus in the first book of On Providence, by Apollodorus in the Physics, and by Posidonius:

​being an animal in this sense, namely an animate, percipient substance. For an animal is superior to that which is not an animal; and nothing is superior to the cosmos; therefore the cosmos is an animal. And that it is animate is clear from our soul being an offshoot from there. Boethus, however, says that the cosmos is not an animal. That it is one is stated by Zeno in On the Whole, and by Chrysippus, Apollodorus in the Physics, and Posidonius in the first book of the Physical Discourse. The "all" is spoken of, as Apollodorus says, as the cosmos, and in another way as the system composed of the cosmos and the external void. The cosmos, then, is finite, but the void is infinite.

​Among the celestial bodies, the fixed stars revolve together with the whole heaven, while the planets move in their own motions. The sun takes an oblique course through the zodiac circle; likewise the moon follows a spiral course. The sun is unmixed fire, as Posidonius says in the seventh book of On Meteorology; and it is larger than the earth, as the same author says in the sixth book of the Physical Discourse; moreover it is spherical, as his followers say, analogous to the cosmos. It is fire, then, because it performs all the operations of fire; it is larger than the earth because the whole of the earth, and indeed the heaven too, is illuminated by it. And the fact that the earth casts a conical shadow indicates that the sun is larger; and it is visible from all sides because of its magnitude.