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. [431] All that
is corporeal is infinitely divisible, although it is never infinitely
divided. [432] At the same time, all things are exposed to the action
of change, since one material is constantly going over into another.
[433] Herein the Stoics follow Aristotle, in contrast to the mechanical
theory of nature, [434] and distinguish change in quality from mere
motion in space. They enumerate several varieties of each kind. [435]
Nevertheless, they look upon motion in space as the primary form of
motion. [436] Under the conception of motion, they, moreover, include
action and suffering. [437] The condition of all action is contact;
[438] 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. [439] 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.
[440] 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, [441] the distance enclosed
within the limits of a body. [442] From Space they distinguish the
Empty. The Empty is not met with in the universe, but beyond the
universe it extends indefinitely. [443] And hence they assert that
Space is limited, like the world of matter, and that the Empty is
unlimited. [444] Nay, not only Space, but Time also, is by them set
down as immaterial; [445] 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. [446]
The Stoics affirm the infinite divisibility of Time and Space, [447]
but do not appear to have instituted any deep researches into this
point.
[B. Elements.]
In expanding their views on the origin of the world, the Stoics begin
with the doctrine of the four elements, [448] 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. [449] 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. [450] 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.
[451] The distinctive characteristic of fire is heat; that of air is
cold; that of water, moisture; dryness that of the earth. [452] These
essential qualities, however, are not always found in the elements to
which they belong in a pure state, [453] and hence every element has
several forms and varieties. [454] 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. [455] 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; [456] water and earth
are drawn towards it; [457] 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. [458] The fire on the circumference goes
by the name of Ether. [459] Its most remote portion was called by Zeno
Heaven; [460] and it differs from earthly fire not only by its greater
purity, [461] but also because the motion of earthly fire is in a
straight line, whereas the motion of the Ether is circular. [462]
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. [463] 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.
[C. The universe.]
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; [464] 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, [465] 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. [466] Thus
the world consists, as with Aristotle, of a globe containing many
strata, one above another. [467] That it cannot be unlimited, as
Democritus and Epicurus maintain, follows from the very nature of body.
[468] The space within the world is fully occupied by the material of
the world, without a vacant space being anywhere left. [469] 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? [470] 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? [471] 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. [472]
[(1) Stars.]
The stars are spherical masses, [473] consisting of fire; but the fire
is not in all cases equally pure, [474] and is sustained, as Heraclitus
taught, by evaporations from the earth and from water. [475] 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. [476] Not only the sun, but the moon also, was
believed to be larger than the earth. [477] 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. [478] The earth,
likewise, is filled by an animating soul; or else how could it supply
plants with animation, and afford nutriment to the stars? [479] Upon
the oneness of the soul, which permeates all its parts, depends, in the
opinion of the Stoics, the oneness of the universe.
[(2) Meteorology.]
Most thoroughly, however, did the Stoics—and, in particular, Posidonius
[480]—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. [481] 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. [482]
Nor need we mention here the somewhat copious writings of Posidonius,
[483] on the subjects of geography, history, and mathematics.
[(3) Plants and animals.]
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.
[484] 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. [485]