Handbook of the History of Logic: - Fordham University Faculty

40 John Marenbon
For day and light are connected to each other, and for this reason the
true propositions of the first and second modes are: ‘If it is day, it
is light’. Then, if someone wants to destroy the truth by adding a
negation, saying, ‘If it is day, it is not light’, the person who adds a
second negation, saying ‘Not if it is day, it is not light’ returns it again
to truth. The first two , therefore, are through the link of
what naturally cohere together (e.g. ‘if it is day, it is light’). The third
through the negation of opposites: e.g. it cannot be that it is day and
it is not light. [Notker, 1882, 612-3]
And another indication of the place of St Gall in this movement is a commentary
probably from the late tenth century on the Isagoge and Categories [Excerpta
Isagogarum, 1995], which is mostly extracted from Boethius’s commentaries (for
the Isagoge, both the first and second are used), but takes the form of a dialogue.
Despite the fact that one of the manuscripts links this commentary with Fleury, in
its earliest form it seems most probably to come from St Gall [Marenbon, 1997a,
26, n. 22]. The commentary also has links with the earlier tradition, though, in
the form of material taken from Alcuin, Boethius’s commentary on Cicero’s Topics
and the Ten Categories [Excerpta Isagogarum, 1995].
4.2 Gerbert of Aurillac
The most famous, by far, of the pioneering logicians of the late tenth century
was Gerbert of Aurillac, who taught at Rheims from 972 until he became the
archbishop there in 991, ending his life as Pope Sylvester (999-1003). There is
an account of his teaching at Rheims by his pupil Richer, which gives some very
precise details:
He ran through dialectic following the order of the books and unravelled
their meaning in clear words. For first the ‘isagoges’, that
is, the Introductions, of Porphyry, using the translation by Victorinus,
the Orator, and then he also explained them according to Boethius.
Following on from this, he expounded Aristotle’s book of the ‘Categories’,
that is, of the predicaments. And he very skilfully showed how
to work at the Periermenias, that is, the book on interpretation. Then
he also made his listeners know about the topics, that is, the seats of
arguments, translated by Cicero from Greek into Latin, and explained
by the Consul Boethius in a commentary of six books. He foresaw
what was useful for the progress of teachers of rhetoric, and he also
usefully lectured on and extracted the meaning from the four books
De topicis differentiis, the two on categorical syllogisms, the three on
hypothetical , the one on definitions and again the one
on divisions. [III, 46-7; Richer, 1877, 101]
Since Richer wrote his account in the years immediately after Gerbert became
archbishop, it should give a faithful account of what Gerbert taught, at least at