Physics 153
growth, the seed can produce each sort of thing, according to its kind-
some things which are nourished only via their roots, others which can
set themselves in motion and perceive and desire and produce others
like themselves. 82. And there are also those who use the term 'nature'
to refer to everything, like Epicurus, who makes the following division:
the nature of all things which exist is bodies and void and their attributes.
But since we say that the cosmos is constituted and governed by nature,
we do not mean that it is like some lump of mud, piece of stone or
anything else with only a natural power of cohesion, but rather that it
is like a tree or animal. For nothing is random in them; rather, it is
evident that they possess a certain orderliness and craftsmanlike quality.
- But if nature's craft is responsible for the life and vigour of plants
which are held together by being rooted in the earth, certainly the earth
itself is held together by the same force, since when the earth is impreg-
nated by seeds she gives birth to and brings forth all things, embraces
their roots, nourishes them, fosters their growth and is herself nourished
in turn by external and superior natural elements. And the air and the
aither and all superior entities are nourished by vapours produced from
the earth. So, if the earth is held together by nature and owes its vigour
to nature, then the same rational force is present in the rest of the cosmos.
For the roots [of plants] are bound to the earth, while animals are sustained
by inhalation of air and the air itself helps us to do our seeing, helps us
to do our hearing and speaking; for none of these functions can be carried
out without air. Indeed, it even helps us to move, since wherever we go
or we move to, it seems to give way and yield to us. - And the motion of things to the central, i.e., lowest, region of the
cosmos, and the motion of other things from the middle to the upper
regions, and the circular orbit of others around this mid point all combine
to make the nature of the cosmos a single and continuous whole. And
since there are four kinds of bodies, nature is rendered continuous by
their mutual interchange. For water comes from earth, air from water
and aither from air; then in reverse air comes from aither, then water
and from water comes earth, the lowest element. Thus the union of the
parts of the cosmos is held together because the elements from which
everything is composed move up and down and back and forth. 85. And
this union must either be everlasting, exhibiting the very order which
we now see, or at the very least very stable, enduring for a long, nearly
boundless expanse of time. And either way it follows that the cosmos is
governed by nature.
Consider the sailing of a fleet of ships, the formation of an army, or
(to return to examples drawn from the works of nature) the reproduction
of vines or trees, or furthermore the shape and organization of the limbs