Handbook of the History of Logic: - Fordham University Faculty

The Assimilation of Aristotelian and Arabic Logic up to the Later Thirteenth Century 303
Great seems to a large extent to have copied many of Kilwardby’s ideas. 53
4.1 Porphyry’s Isagoge and Aristotle’s Categories
Porphyry’s Isagoge was written as an introduction to the Categories and it was
treated as such in the Middle Ages. It was usually the first logic text university
students met in the thirteenth century. It was also important because it gave
medieval authors an opportunity to comment on universals. This is not because
there is an account of universals in Isagoge, since there is none, but because the
three “hard questions” that Porphyry states in the beginning. He writes:
For example, I shall beg off saying anything about (a) whether genera
and species are real or are situated in bare thoughts alone, (b) whether
as real they are bodies or incorporeals, and (c) whether they are separated
or in sensibles and have their reality in connection with them.
Such business is profound, and requires another, greater investigation.
Instead I shall now try to show how the ancients, the Peripatetics
among them most of all, interpreted genus and species and the other
matters before us in a more logical fashion. 54
The way one answers these questions will determine what view of universals one
ends up with, and just by stating these questions Porphyry had a profound influence
on medieval philosophy and logic. It was, however, Boethius that first
attempted an answer. 55
To many scholars disappointment Averroes chose to ignore these questions in
his middle commentary on Isagoge, and one of the first that commented on the
work in the thirteenth century was Robert Kilwardby. Among his teachings is a
course on the logica vetus, which contains lectures on the Isagoge, Categories and
De interpretatione. 56
Kilwardby addresses Porphyry’s questions in the introduction to his commentary.
He thinks universals have an existence as forms in singulars, and have a
unity based on agreement in essence. He also argues that the ideas in the mind of
God are formal causes and exemplars of the universals. In human cognition, the
universals (the forms) are abstracted from then individuals they exist in. Universals
must be in singulars he argues, since the singulars would otherwise not make
any contribution to the signification of a universal.
Following Avicenna, Kilwardby contrasts the metaphysicians approach to universals
and the logicians. In metaphysics, universals are studied in abstraction
from language, while in logic they are studied as having a nature connected with
language. Universals are names that can be predicated for the logician, but their
existence is prior to language, and the signification is derived from the real form.
53See [Ebbesen, 1981b; Lagerlund, 2000, Chapter 2; Thom, 2007].
54Spade [1994, 1].
55See [Klima, 2004] for a outline of the history of universals in medieval philosophy.
56See [Lewry, 1981] for a discussion of the content of this course.