If it were our opinion that essence was one, we would not need to study
whether there was one single genus for all things, whether all genera
could not be reduced to a single one; whether there were principles;
whether the genera were at the same time principles; or whether all
principles are genera, without saying conversely that all genera are
principles; or, if we must distinguish between them, say that some
principles are simultaneously genera, or some genera are principles,
or, finally, whether all principles be genera without the genera being
principles, and conversely. But, since we do not acknowledge that
essence is one, the reasons[298] for which were advanced by Plato
and other philosophers, we find ourselves forced to treat all these
questions, and first to explain why we recognize genera of essences,
and what number we decide on.