7. Why is the existence of both good and evil necessary? Because
matter is necessary to the existence of the world. The latter is
necessarily composed of contraries, and, consequently, it could not
exist without matter. In this case the nature of this world is a
mixture of intelligence and necessity.[179] What it receives from
divinity are goods; its evils derive from the primordial nature,[180]
the term used (by Plato) to designate matter as a simple substance yet
unadorned by a divinity. But what does he mean by "mortal nature?"
When he says that "evils besiege this region here below," he means the
universe, as appears from the following quotations[181]: "Since you
are born, you are not immortal, but by my help you shall not perish."
In this case it is right to say that evils cannot be annihilated. How
then can one flee from them?[182] Not by changing one's locality, (as
Plato) says, but by acquiring virtue, and by separating from the body,
which, simultaneously, is separation from matter; for being attached
to the body is also attachment to matter. It is in the same sense that
(Plato) explains being separated from the body, or not being separated
from it. By dwelling with the divinities he means being united to the
intelligible objects; for it is in them that inheres immortality.