CHAPTER VIII.. Irrational Nature. the Elements. the Universe.

IRRATIONAL NATURE. THE ELEMENTS. THE UNIVERSE.

Turning from the questions which have hitherto engaged our attention to natural science in the stricter sense of the term, we must first touch upon [A. The most general ideas on nature.] a few characteristic questions affecting the general conditions of all existence. In these the Stoics hold little that is of a distinctive character. The matter or substance of which all things are made is corporeal. All that is corporeal is infinitely divisible, although it is never infinitely divided. At the same time, all things are exposed to the action of change, since one material is constantly going over into another. Herein the Stoics follow Aristotle, in contrast to the mechanical theory of nature, and distinguish change in quality from mere motion in space. They enumerate several varieties of each kind. Nevertheless, they look upon motion in space as the primary form of motion. Under the conception of motion, they, moreover, include action and suffering. The condition of all action is contact; and since the motions of different objects in nature are due to various causes, and have a variety of characters, the various kinds of action must be distinguished which correspond with them. In all these statements there is hardly a perceptible deviation from Aristotle.

Of a more peculiar character are the views of the Stoics as to the intermingling of substances, to which reference has already been made. With regard to Time and Space, they found some innovations on Aristotle’s theory to be necessary. Space (τόπος), according to their view, is the room occupied by a body, the distance enclosed within the limits of a body. From Space they distinguish the Empty. The Empty is not met with in the universe, but beyond the universe it extends indefinitely. And hence they assert that Space is limited, like the world of matter, and that the Empty is unlimited. Nay, not only Space, but Time also, is by them set down as immaterial; and yet to the conception of Time a meaning as concrete as possible is given, in order that Time may have a real value. Zeno defined Time as the extension of motion; Chrysippus defines it, more definitely, as the extension of the motion of the world. The Stoics affirm the infinite divisibility of Time and Space, but do not appear to have instituted any deep researches into this point.

In expanding their views on the origin of the world, the Stoics begin with the doctrine of the four elements, a doctrine which, since the time of Aristotle and Plato, was the one universally accepted. They even refer this doctrine to Heraclitus, desiring, above all things, to follow his teaching in natural science. On a previous occasion, the order and the stages have been pointed out, according to which primary fire developed into the several elements in the formation of the world. In the same order, these elements now go over one into the other. Yet, in this constant transformation of materials, in the perpetual change of form to which primary matter is subject, in this flux of all its parts, the unity of the whole still remains untouched. The distinctive characteristic of fire is heat; that of air is cold; that of water, moisture; dryness that of the earth. These essential qualities, however, are not always found in the elements to which they belong in a pure state, and hence every element has several forms and varieties. Among the four essential qualities of the elements, Aristotle had already singled out two, viz. heat and cold, as the active ones, calling dryness and moisture the passive ones. The Stoics do the same, only more avowedly. They consider the two elements to which these qualities properly belong to be the seat of all active force, and distinguish them from the other two elements, as the soul is distinguished from the body. In their materialistic system, the finer materials, as opposed to the coarser, occupy the place of incorporeal forces.

The relative density of the elements also determines their place in the universe. Fire and air are light; water and earth are heavy. Fire and air move away from the centre of the universe; water and earth are drawn towards it; and thus, from above to below—or, what is the same thing, from without to within—the four layers of fire, air, water, and earth are formed. The fire on the circumference goes by the name of Ether. Its most remote portion was called by Zeno Heaven; and it differs from earthly fire not only by its greater purity, but also because the motion of earthly fire is in a straight line, whereas the motion of the Ether is circular. Because of this difference of motion, Aristotle supposed a radical difference to exist between these two kinds of fire, but the Stoics did not feel it necessary to admit such a difference. They could always maintain that, when beyond the limits of its proper locality, fire tried to return to it as quickly as possible, whereas within those limits it moved in the form of a circle.

Holding this view of the elements, the Stoics, it will be seen, did not deviate to any very great extent, in their ideas of the World, from Aristotle and the views which were generally entertained. In the centre of the Universe reposes the globe of the earth; around it is water, above the water is air. These three strata form the kernel of the world, which is in a state of repose, and around these the Ether revolves in a circle, together with the stars which are set therein. At the top, in one stratum, are all the fixed stars; under the stratum containing the fixed stars are the planets, in seven different strata—Saturn, Jupiter, Mars, Mercury, Venus, then the Sun, and in the lowest stratum, bordering on the region of air, is the Moon. Thus the world consists, as with Aristotle, of a globe containing many strata, one above another. That it cannot be unlimited, as Democritus and Epicurus maintain, follows from the very nature of body. The space within the world is fully occupied by the material of the world, without a vacant space being anywhere left. Outside the world, however, is empty space, or else how—the Stoics asked—would there be a place into which the world could be resolved at the general conflagration? Moreover, this empty space must be unlimited; for how can there be a limit, or any kind of boundary, to that which is immaterial and non-existent? But although the world is in empty space, it does not move, for the half of its component elements being heavy, and the other half light, as a whole it is neither heavy nor light.

The stars are spherical masses, consisting of fire; but the fire is not in all cases equally pure, and is sustained, as Heraclitus taught, by evaporations from the earth and from water. With this process of sustentation the motion of the stars is brought into connection, their orbit extending over the space in which they obtain their nutriment. Not only the sun, but the moon also, was believed to be larger than the earth. Plato and Aristotle had already held that the stars are living rational divine beings; and the same view was entertained by the Stoics, not only because of the wonderful regularity of their motion and orbits, but also from the very nature of the material of which they consist. The earth, likewise, is filled by an animating soul; or else how could it supply plants with animation, and afford nutriment to the stars? Upon the oneness of the soul, which permeates all its parts, depends, in the opinion of the Stoics, the oneness of the universe.

Most thoroughly, however, did the Stoics—and, in particular, Posidonius —devote themselves to investigating those problems, which may be summed up under the name of meteorology. This portion, however, of their enquiries is of little value for illustrating their philosophical tenets, and it may suffice to mention in a note the objects which it included, and the sources whence information may be obtained. The same treatment may be given to the few maxims laid down by the Stoics on the subject of inorganic nature which have come down to us. Nor need we mention here the somewhat copious writings of Posidonius, on the subjects of geography, history, and mathematics.

Little attention was devoted by the Stoics to the world of plants and animals. About this fact there can be no doubt, since we neither hear of any treatises by the Stoics on this subject, nor do they appear to have advanced any peculiar views. The most prominent point is, that they divided all things in nature into four classes—those of inorganic beings, plants, animals, and rational beings. In beings belonging to the first class a simple quality (ἕξις) constitutes the bond of union; in those of the second class, a forming power (φύσις); in those of the third class, a soul; and in those of the fourth class, a rational soul. By means of this division, the various branches of a science of nature were mapped out, based on a gradually increasing development of the powers of life. No serious attempt was made by the Stoics to work out this thought. With the single exception of man, we know exceedingly little of their views on organic beings.