The Lives and Opinions of Eminent Philosophers by Diogenes Laërtius (best free ebook reader txt) 📕

species; but according to genera they divide them into three topics: that of the world, that of the elements, and the third is that which reasons on causes. The topic about the world, they say, is subdivided into two parts: For that in one point of view, the mathematicians also have a share in it; and according to it it is that they prosecute their investigations into the nature of the fixed stars and the planets; as, for instance, whether the sun is of such a size as he appears to be, and similarly, whether the moon is; and in the same way they investigate the question of spherical motion, and others of the same character. The other point of view is that which is reserved exclusively for natural philosophers, according to which it is that the existence and substance of things are examined [for instance, whether the sun and the stars consist of matter and form], and whether the sun is born or not born, whether it is living or lifeless, corruptible or incorruptible, whether it is regulated by Providence, and other questions of this kind.

The topic which examines into causes they say is also divisible into two parts; and with reference to one of its considerations, the investigations of physicians partake of it; according to which it is that they investigate the dominant principle of the soul, and the things which exist in the soul, and seeds, and things of this kind. And its other division is claimed as belonging to them also by the mathematicians, as for instance how we see, what is the cause of our appearance being reflected in a mirror, how clouds are collected, how thunder is produced, and the rainbow, and the halo, and comets, and things of that kind.

They think that there are two general principles in the universe: the active and the passive. That the passive is matter, an existence without any distinctive quality. That the active is the reason which exists in the passive, that is to say, God. For that he, being eternal, and existing throughout all matter, makes everything. And Zeno of Citium lays down this doctrine in his treatise on Essence, and so does Cleanthes in his essay on Atoms, Chrysippus in the first book of his Investigations in Natural Philosophy towards the end, Archedemus in his work on Elements, and Posidonius in the second book of his treatise on Natural Philosophy. But they say that principles and elements differ from one another. For that the one had no generation or beginning, and will have no end; but that the elements may be destroyed by the operation of fire. Also, that the elements are bodies, but principles have no bodies and no forms, and elements too have forms.

Now a body, says Apollodorus in his Natural Philosophy, is extended in a threefold manner: in length, in breadth, in depth; and then it is called a solid body; and the superficies is the limit of the body having length and breadth alone, but not depth. But Posidonius, in the third book of his Heavenly Phenomena, will not allow a superficies either any substantial reality, or any intelligible existence. A line is the limit of a superficies, or length without breadth, or something which has nothing but length. A point is the boundary of a line, and is the smallest of all symbols.

They also teach that God is unity, and that he is called Mind, and Fate, and Jupiter, and by many other names besides. And that as he was in the beginning by himself, he turned into water the whole substance which pervaded the air; and as the seed is contained in the produce, so too, he being the seminal principle of the world, remained behind in moisture, making matter fit to be employed by himself in the production of those things which were to come after; and then, first of all, he made the four elements: fire, water, air, and earth. And Zeno speaks of these in his treatise on the Universe, and so does Chrysippus in the first book of his Physics, and so does Archedemus in some treatise on the Elements.

Now an element is that out of which at first all things which are are produced, and into which all things are resolved at last. And the four elements are all equally an essence without any distinctive quality, namely, matter; but fire is the hot, water the moist, air the cold, and earth the dry⁠—though this last quality is also common to the air. The fire is the highest, and that is called aether, in which first of all the sphere was generated in which the fixed stars are set, then that in which the planets revolve; after that the air, then the water; and the sediment as it were of all is the earth, which is placed in the center of the rest.

They also speak of the world in a threefold sense; at one time meaning God himself, whom they call a being of a certain quality, having for his peculiar manifestation universal substance, a being imperishable, and who never had any generation, being the maker of the arrangement and order that we see; and who, after certain periods of time, absorbs all substance in himself and then reproduces it from himself. And this arrangement of the stars they call the world, and so the third sense is one composed of both the preceding ones. And the world is a thing which is peculiarly of such and such a quality consisting of universal substance, as Posidonius affirms in his Meteorological Elements, being a system compounded of heaven and earth, and all the creatures which exist in them; or it may be called a system compounded of Gods and men, and of the things created on their account. And the heaven is the most remote circumference of the world, in which all the Divine Nature is situated.

Again, the world is inhabited