1. Very ancient philosophers have investigated the number and kinds
of essences. Some said there was but one;[296] others, that there was
a limited number of them; others still, an infinite number. Besides,
those who recognized but a single (essence) have advanced opinions very
different, as is also the case with those who recognized a limited or
unlimited number of essences. As the opinions of these philosophers
have been sufficiently examined by their successors, we shall not
busy ourselves therewith. We shall study the doctrine of those who,
after having examined the opinions of their predecessors, decided on
determinate numbers (of essences); admitting neither a single essence,
because they recognized that there was a multiplicity even in the
intelligibles; nor an infinite number of essences, because such an
infinity could not exist, and would render all science impossible; but
who, classifying the essences whose number is limited, and seeing that
these classifications could not be considered elements, looked on them
as "kinds." Of these, some (the Peripatetic Aristotelians) proposed
ten, while others proposed a lesser number (the Stoics taught four), or
a greater number (the Pythagorean "oppositions," for instance). As to
the kinds, there is also difference of opinions: some looked upon the
kinds as principle (Plotinos himself); while others (Aristotle) held
that they formed classes.