[998b]
[1]
he observes, e.g., of what parts a bed consists and
how they are put together; and then he comprehends its nature. Thus to
judge from these arguments the first principles will not be the genera
of things.But from the point of view
that it is through definitions that we get to know each particular
thing, and that the genera are the first principles of definitions,
the genera must also be the first principles of the things
defined.And if to
gain scientific knowledge of things is to gain it of the species after
which things are named, the genera are first principles of the
species. And apparently some even of those1 who call Unity
or Being or the Great and Small elements of things treat them as
genera.Nor again is it possible
to speak of the first principles in both senses.The formula of substance is one; but
the definition by genera will be different from that which tells us of
what parts a thing is composed.Moreover, assuming that the genera are first
principles in the truest sense, are we to consider the
primary genera to be first principles, or the final terms
predicated of individuals? This question too involves some
dispute.For if
universals are always more truly first principles, clearly the answer
will be "the highest genera," since these are predicated of
everything. Then there will be as many first principles of
things
[20]
as there are
primary genera, and so both Unity and Being will be first principles
and substances, since they are in the highest degree predicated of all
things.But it is
impossible for either Unity or Being to be one genus of existing
things. For there must be differentiae of each genus, and
each differentia must be one2; but it is impossible either for the
species of the genus to be predicated of the specific differentiae, or
for the genus to be predicated without its species.3 Hence if
Unity or Being is a genus, there will be no differentia Being or
Unity.But if they
are not genera, neither will they be first principles, assuming that
it is the genera that are first principles. And further, the
intermediate terms, taken together with the differentiae, will be
genera, down to the individuals; but in point of fact, although some
are thought to be such, others are not. Moreover the differentiae are
more truly principles than are the genera; and if they also are
principles, we get an almost infinite number of principles, especially
if one makes the ultimate genus a principle.
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