Handbook of the History of Logic: - Fordham University Faculty

122 Ian Wilks
supply these criteria. As such it serves as an ars iudicandi, a technique for judging.
But it can also be construed as an ars inveniendi, a technique for inventing.
Instead of just providing constraints on what counts as a successful argument, it
may additionally be expected to provide guidance on how to construct a successful
argument in the first place, given the desired conclusion [Boethius, 1990, p. 1
(4–5)].
The historically seminal text for logic taken in this less common, creative role is
Aristotle’s Topics. Here we find, in somewhat loosely gathered form, advice on how
to advance from the yes- or the no-position on a debatable yes-or-no question to an
argument for that position. This advance happens through analysis of the relation
between the subject and predicate terms of the proposition which expresses that
position. Propositions involving different kinds of predicative relation and different
kinds of subject matter will necessitate different kinds of advice; the basic unit
of advice is referred to as a topic, or, in the Latin, a locus. There are, of course,
many topics, and the challenge of the commentators is to impose some order on
this profusion of material.
Topics for Aristotle come in the form of a general instruction for argument
formation, with some kind of accompanying reason for the instruction. 75 Or they
come in the form of an instruction alone without the reason, or just as a reason
expressed in such a way as to suggest the instruction which it justifies [Green-
Pedersen, 1984, p. 21]. Boethius tries to standardize this presentation of the
topics by using two key organizing conceptions: the maxima propositio (“maximal
proposition”), and the differentia (distinguishing principle). I will consider these
in turn.
The maximal proposition is the principle which shows the arguer how to identify
a salient fact about one of the terms: a fact which reveals how that term may be
put in the desired predicative relation to the other term. Here are some Boethian
examples of maximal propositions. (i) Say one wishes to show that trees are
not animals. This may be derived by using the following principle, i.e., maximal
proposition: What the definition of the genus does not belong to is not a species
of the genus defined [Boethius, 1990, pp. 29 (18–19)]. With this principle in view
one may then note that an animal is an animate substance capable of perceiving,
and further that a tree is not an animate substance capable of perceiving. The
conclusion follows from the maximal proposition plus the two ensuing facts. (ii)
Say one wishes to show that justice is natural. This maximal proposition will serve:
Those things whose efficient causes are natural are themselves natural [Boethius,
1990, p. 35 (9–10)]. With this principle in view one may then note that the
society of men is natural, and further that the society of men is the efficient cause
of justice. The conclusion follows from the maximal proposition plus the two
ensuing facts. (iii) Say one wishes to argue that the rulers of cities should not be
chosen by lot. This maximal proposition will serve: What occurs in a thing must
75 In [Stump, 1978, p. 167] we find a slightly different language for expressing this distinction:
she speaks of “a strategy or line of argument or tack to take” as opposed to “a principle or a law
that explains or justifies the strategy.”