Handbook of the History of Logic: - Fordham University Faculty

84 Ian Wilks
question. 2 And second, there is the Dialectica, a single work which does not take
the explicit form of a commentary, but nonetheless is closely organized around
the content of several of the above ancient sources. 3 My discussion of Abelard’s
logical theory will be based chiefly on these two works 4 . Note that Abelard was a
reasonably prolific author, and produced a wealth of additional material, notably
an early set of commentaries on Isagoge, De interpretatione, andDe divisione, an
extremely valuable later commentary on the Isagoge (which goes under the name
Logica nostrorum petitioni sociorum), a brief treatise on abstraction and knowledge
(Tractatus de intellectibus), as well as quite a number of works in biblical
exegesis, theology and ethics. 5
About halfway through the Dialectica we find a passage which explains the organizing
principle behind its presentation of logical theory: “Just as before defining
the categorical syllogisms it was appropriate for their content in categorical propositions
to be treated, in the same way it is necessary that before defining hypothetical
syllogisms their hypothetical propositions . . . be treated” [Abelard, 1970, p.
253 (4–7)]. What is suggested here is the appropriateness of presenting logical theory
in two sequences, both culminating with discussion of syllogisms. In the first
sequence the structure of categorical propositions is discussed to provide insight
into categorical syllogisms. In the second the structure of hypothetical propositions
is discussed to provide insight into hypothetical syllogisms. But of course
what is ideal for both kinds of syllogisms is to have true propositions [Abelard,
1970, p. 253 (7–9)]. So we can take the grounding investigation one step further
in each case. What makes categorical and hypothetical propositions true? For the
truth of categorical propositions we look to their constituent words. And for the
truth of hypotheticals, Abelard says, we look to their corresponding topics. 6
It is standard practice to develop an account of categorical logic which starts
with a discussion of words, and moves through categorical propositions to the categorical
syllogisms themselves. Abelard consciously adopts a parallel course for
the logic of hypotheticals by beginning with a treatment of topics and hypothetical
propositions. In general we can think of Abelard’s development of material
as falling along these two axes: discussion of words and categorical propositions
leading to categorical syllogisms; and then discussion of topics and hypothetical
2 For the view that he did so intend see [Marenbon, 1997a, pp. 47–8].
3 The relative dating of these texts has been subject to debate. I accept the conclusions
drawn in [Mews, 1985, 126–27], which hold the Dialectica tobeearlierthantheglossesofLogica
ingredientibus. Brief summaries of other positions on this question are available in [de Rijk, 1970,
pp. xxi–xxiii] and [Mews, 1987, p. 16, note 2].
4 In particular my discussion will draw heavily from the commentary on De interpretatione
in Logica ingredientibus; this commentary goes by the name Glossae super Periermeneias Aristotelis.
An overview of current scholarship on the contents of Abelard’s logical works is found in
[Marenbon, 2006, pp. 333–342].
5 For a list see [Marenbon, 1997a, pp. xvi–xix]. Certain works of Abelard are lost; see [Van
den Eynde, 1962] and [Mews, 1985].
6 What is meant by “topic” in this context is, of course, not self-evident, and will be fully
treated in Part 2 below. Technically speaking, the label “hypothetical” includes disjunctions as
well as conditionals for Abelard, so it is necessary to specify that, in this paragraph and the next,
“hypothetical” is to be taken as meaning “conditional.”