CHAPTER XXX ---- WHAT IS THE SUBSTANCE OF THE PLANETS AND FIXED STARS?
'THALES: the heavenly bodies are of earth, but on fire.
'Empedocles: of fire, from the fiery element, which the air contained in itself and thrust out at the first separation of the elements.
'Anaxagoras: the surrounding atmosphere is in its substance fire, but by the energy of its revolution catches up stones from the earth, and having set them on fire has made stars of them.;
'Diogenes: the heavenly bodies are porous like pumice, and are the breathing-holes of the universe. But again the same author thinks that they are stones, which, though at first invisible, often fall upon the Earth and are extinguished, just as the stony meteor which fell in a fiery form at Aegospotamoi.
'Empedocles: the fixed stars are fastened to the crystalline sphere, but the planets are free.
'Plato: for the most part they are of fire, but partake also of the other elements as a cement.
'Xenophanes: they consist of clouds on fire, but are extinguished every day, and re-kindled in the night, just like live coals: for their risings and settings are their kindlings and quenchings.
'Heracleides and the Pythagoreans think that each of the stars is a world, including an Earth, and an atmosphere and an ether in the infinite space. These doctrines are introduced in the Orphic Hymns, for they make each star a world.
'Epicurus rejects none of these opinions, but adheres to his "possible."'