and subject-matter in the treatises as we have them cata-
logued by Andronicus of Rhodes. And, though there is no
evidence for such a physical arrangement in the treatises
themselves, nor any statements from Aristotle to demand
such an order of treatment, such a disposition of the treatises
was quite probably traditional and it does have the sanction
of the Lyceum and later Peripatetics. The Categories may
not have been written by Aristotle himself, though some of
the reasons presented to substantiate this surmise are not
at all scientifically conclusive. But whatever the status of
the categories as to their actual composer, it is quite clear
that the ideas emphasized are, for the most part, in com-
plete accord with the general philosophical teaching found
elsewhere in the Aristotelian corpus. The division of the
ten categories is repeated by name in The Topics, eight
are again mentioned in the Physics and Posterior Analytics
in a context where the remaining two were not a propos
to the subject being discussed and seven are repeated in
the Metaphysics under similar circumstances. All in all I
would consider that the contents of the treatise entitled
The Categories is Aristotelian and helpful as a propaedeutic
to the other works of Aristotle.

The central core of the Organon is concerned with scien-
tific proof. Scientific proof is a demonstration in which cer-
tain things being given something else necessarily follows;
its external form is the syllogism. Scientific proof concerns
necessary conclusions derived necessarily from premises
which themselves involve true and necessary matter. It is
quite clear, then, that science is the power or virtue of the
mind which involves conclusions of this special type; it is
a quality of the first grade, acquired by repeated exercise,
which makes the knower proficient as regards deriving scien-
tific conclusions. Hence the essential core of the Organon
is duplex: the Prior and Posterior Analytics, the former
concerned with the pattern and the latter with the subject-
matter of scientific proof. Like the middle term in a perfect
syllogism these two treatises are middle in position as well

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