1. The Character of Logic
l(a) Aristotle's logic
This volume studies logic in the broad sense that corresponds to Aristotle's logical
works and includes, as we shall see, a certain amount of metaphysics. Porphyry
wrote an
Introduction
(Eisag6g6, sometimes written as Isagoge), also called in
Latin the Five Expressions
(Quiitque
Voces), because it discusses five key terms:
genus, species, differentia, property and accident. He intended it to throw light on
Aristotle's categories and on definition, division and demonstration. The Isagoge
itself became the subject of commentaries, and the commentators saw it as useful
for the whole of philosophy. It will be drawn on here especially for its important
remarks on universals and particulars.
The standard order of Aristotle's writings was, at least until a recent sceptical
article,' thought to have been established by the first of the commentators of the
Aristotelian school, Andronicus, around 60 BC. According to the standard explana-
tion, we start with Aristotle's
Categories, because this discusses individual terms,
arranging them into categories, starting with substance, quantity, quality, relative.
On the question whether the terms are words, concepts, or things, Porphyry's
compromise came to be orthodox among later Greek commentators: they are
words
insofar as they
signify thii~gs.~ The distinction of categories might well be classified
nowadays as a piece of metaphysics, but if so, Porphyry's insistence remains
important, that the discussion concerns only the metaphysics of the
sensible world."
In Neoplatonism, the sensible world is produced by a higher intelligible world and
these two worlds constitute a universe of beings which the Neoplatonists regard as
conscious. Hence the metaphysics of the Neoplatonist universe is further revealed
through the readings in the
Psychology volume.
Aristotle's second work in the standard arrangement is
On Interpretation, in
which he studies the logical relations and truth values of whole propositions, but
especially4 of pairs of opposed propositions. He has to preface this study with a brief
distinction of name and verb and a brief, but extremely influential, discussion of
the meaning of words.
In a work standardly placed fifth (though Adrastus disagreed,
up. Simplicium
in Cat. 16,1), the Topics, Aristotle exploits the discussion of opposed propositions
by providing a handbook of rules for dialectical debate. It is here that Porphyry's
distinction of five expressions is most fully explained, since an analogous set of four
so-called predicables, genus, definition, peculiar property, and accident, form the
subject matter of dialectical debate. The purposes of dialectical debate range Grom
the discovery of the first principles of science to countering the tricks of sophists.
Of the former an example would be the discussion in
Physics Book 4 of the nature
of place and time. This is discovered through a number of considerations such as
would arise in dialectical debate with another person, or with oneself. The latter is
discussed in what is sometimes treated as the ninth book of the
!ltpics and
sometimes as a separate work,
On Sophistical
Refzctations.
In the work standardly placed third, the Bior Analytics, Aristotle expounds his
great discovery, the deductive syllogism, the pattern of argument in which he
distinguished fourteen valid moods, arranged into three figures. Aristotle also