On the contrary, in the system of Aristotle, the immutability of the
stars is easily explained, but only after accepting his theory of a
fifth element (the quintessence[205]). If, however, it be rejected,
it would be impossible to demonstrate that the heaven, let alone its
parts, the sun and the stars, do not perish, while (as Aristotle does)
we regard the body of the heaven as being composed of the same elements
as terrestrial animals.
PLOTINOS'S VIEWS SUPPORTED BY THE HEAVEN'S POSSESSION OF THE SOUL AND
BODY.
As every animal is composed of soul and body, the heaven must owe the
permanence of its individuality to the nature either of its soul, or
of its body; or again, to that of both. On the hypothesis that its
incorruptibility is due to the nature of its body, the Soul's only
function will be to animate it (by uniting with the body of the world).
On the contrary hypothesis that the body, by nature corruptible,
owes its incorruptibility exclusively to the Soul, there is need of
demonstration that the state of the body does not naturally oppose
this constitution and permanence (for, naturally constituted objects
admit of no disharmony); but that, on the contrary, here matter, by
its predisposition, contributes to the accomplishment of the divine
volition.