Zeno of Citium: Founder of Stoicism

⁶⁷ The Stoics divide natural philosophy into the topics of:

• bodies
• principles
• elements
• Gods
• boundaries
• place
• the vacuum.

They make these divisions according to species. But according to genera they divide them into 3 topics:

1. The world

This is divided into 2:

• Mathematical
• Philosophical as existence and substance

2. The elements

3. Causes

This is also divisible into 2:

• the soul based causes

• 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.

LXVIII. The believe in 2 general principles in the universe:

1. The passive

This is matter, an existence without any distinctive quality.

2. The active

This 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.

Zeno, the Cittiæan, 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.

Apollodorus in his Natural Philosophy says that a solid body is extended in a threefold manner: length, breadth, depth.

The surface is the limit of the body having length and breadth alone, but not depth.

But Posidonius, in book 3 of his Heavenly Phænomena, will not allow a surfaces 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.
• was in the beginning by himself, he turned into water the whole substance which pervaded the air

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 4 elements, fire, water, air, and earth.

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.

LXIX. An element is that out of which at first all things which are are produced, and into which all things are resolved at last.

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 æther, 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 centre of the rest.