Handbook of the History of Logic: - Fordham University Faculty

546 Simo Knuuttila
in the first or second way (cf. Aristotle, An. post. I.4) and consequently necessary
per se and not merely per accidens. Similarly Kilwardby states that in
mixed first-figure syllogisms with contingent and assertoric premises the assertoric
premise must be simply assertoric, but now not necessary. It is simply assertoric
if the predicate belongs to the subject essentially, invariably or by natural contingency.
146 Kilwardby states that even though the conclusions in mixed first-figure
necessary-assertoric moods and mixed assertoric-necessary moods with simply assertoric
premises are necessary, they are syllogistically derived as necessary only
in the first case. The modal character of the predicate in the conclusion of perfect
first-figure syllogisms follows that of the first premise which involves the whole
syllogism in accordance with the dici de omni et nullo. 147
In explaining the varieties in reading assertoric premises in mixed syllogisms,
Kilwardby states that a first-figure major necessity premises ‘appropriates’ to itself
a minor which is unrestrictedly assertoric, i.e., necessary per se. No such appropriation
occurs in first-figure mixed assertoric-necessity syllogisms, the first premise
being either necessary or true as-of-now. In the second figure, while the universal
negative necessity premise appropriates to itself an unrestricted assertoric premise,
a particular necessity premise cannot appropriate a universal to itself, nor an affirmative
a negative. There are similar considerations about third-figure moods. 148
In uniform contingency syllogisms, the subject term of the major premise is
read ‘Everything/something that is contingently A’ but this ampliation does not
concern mixed contingency syllogisms. 149 This major contingency premise is always
false when the subject is an accidental term and the predicate a substantial
term. If the same applies to contingent minor premises, it seems that a major
premise can be true with a minor only when the middle term is accidental, taking
for granted that both terms cannot be substantial in a true contingency proposition.
Kilwardby explains, however, that if the subject term of the minor premise
is not ampliated, it may be true even when the predicate is a substantial term. 150
Kilwardby’s considerations show similarities to Averroes’s classification of modal
propositions with essential and accidental terms. Both authors assume that propositions
of the same form can have different interpretations depending on how they
are related to other propositions in a syllogism. These interpretation rules are
based on various metaphysical assumptions. Kilwardby’s ad hoc remarks on contingency
premises read in the sense of natural contingency in certain moods show
the same approach. 151
146Kilwardby, In In Pr. an. 16va; 25rb; see also Albert the Great, In In Pr. an. IV.10,
558b-559b.
147Kilwardby, op. cit. 16vb-17ra; 21ra-b; Albert the Great, op. cit. IV.4, 526a-b. For the
application of the dici de omni et nullo in this context, see also Lagerlund 2001, 41-2.
14816vb; 17va-b; 18vb; 24vb. See also Thom 2007, 148, 160-1, 165-6, 172-4ch. 5.
149Kilwardby, op. cit. 19vb, 21ra-b; Albert the Great, op. cit. IV.2, 540b-541a.
150Kilwardby, op. cit. 22ra; Albert the Great, op. cit. IV.4, 545a-b.
151In a mixed first-figure necessity-contingency mood the first negative premise ‘appropriates’