The Stoics assign the first rank to substances, and place matter before
the other substances. From this it results that the Stoics assign to
the same rank their first Principle, and with it the things which are
inferior thereto. First, they reduce to a single class both anterior
and posterior things, though it be impossible to combine them in this
manner. In fact, every time that things differ from each other in that
some are anterior, and others posterior, those which are posterior owe
their essence to those which are anterior. On the contrary, when things
are comprised within one and the same class, all equally owe their
essence to this class, since a class is "what is affirmed of kinds of
things in regard to essence." The Stoics themselves recognize this by
saying that all things derive their essence from matter.
Besides, when they count but a single substance, they do not enumerate
the beings themselves, but they seek their principles. Now there is a
great difference between treating of principles and treating of beings.
If the Stoics recognize no essence other than matter, and think that
other things are modifications of matter, they are wrong in reducing
essence and other things to a common class; they should rather say
that essence is being, and that other things are modifications, and
then distinguish between these modifications. Further, it is absurd to
assert that (among essences), some should be substances, and others
should be other things (such as qualities, modes and relations); for
the Stoics recognize but a single substance, which does not contain any
difference, unless by division as of mass into parts; besides, they
should not attribute divisibility to their substance, because they
teach that it is continuous. They should therefore say, "substance"
(and not "substances").