terpretation_," investigates language as the
expression of thought; and inasmuch as a true or false thought must be
expressed by the union or separation of a subject and a predicate, he
deems it necessary to discuss the parts of speech--the general term and
the verb--and the modes of affirmation and denial. In this treatise he
develops the nature and limitations of propositions, the meaning of
contraries and contradictions, and the force of affirmations and denials
in _possible, contingent_, and _necessary_ matter.

The third are the "_Analytics_," which show how conclusions are to be
referred back to their principles, and arranged in the order of their
precedence.

The First or Prior Analytic presents the universal doctrine of the
Syllogism, its principles and forms, and teaches how must reason, if we
would not violate the laws of our own mind. The theory of reasoning,
generally, with a view to accurate demonstration, depends upon the
construction of a perfect syllogism, which is defined as "a discourse in
which, certain things being laid down, something else different from the
premises necessarily results, in consequence of their existence."[693]
Conclusions are, according to their own contents and end, either
_Apodeictic_, which deal with necessary and demonstrable matter, or
_Dialectic_, which deal with probable matter, or _Sophistical_, which
are imperfect in matter or form, and announced, deceptively, as correct
conclusions, when they are not. The doctrine of Apodeictic conclusions
is given in the "_Posterior Analytic_," that of Dialectic conclusions in
the "_Topics_," and that of the Sophistical in the "_Sophistical
Elenchi_."

Now, if Logic is of any value as an instrument for the discovery of
truth, the attainment of certitude, it must teach us not only how to
deduce conclusions from premises, but it must certify to us the validity
of the principles from whence we reason and this is attempted by
Aristotle in the Posterior Analytic. This treatise opens with the
following statement: All doctrine, and all intellectual discipline,
arises from a prior or pre-existent knowledge. This is evident, if we
survey them all; for both mathematical sciences, and also each of the
arts, are obtained in this manner. The same holds true in the case of
reasonings, whether through [deductive] _Syllogism_ or through
_Induction_, for both accomplish the instruction they afford from
information previously known--the former (syllogi