Handbook of the History of Logic: - Fordham University Faculty

642 E. Jennifer Ashworth
By this he seems to mean that it would be plausible for people to act in that
way. His example is “Caesar is seeking munitions, therefore he will become a
tyrant”, where the suppressed premiss is “All those who seek munitions are aiming
to become tyrants.” He goes on to argue that such consequences obey the
regulative principle that the negation of the consequent appears to be inconsistent
(verisimiliter repugnat) with the antecedent, but while we can call them rhetorical,
simply speaking they are just invalid and non-necessary. 162
I confess that I have not done a complete survey of sixteenth-century logical
literature. However, based on the evidence so far, I think it fair to conclude that
the view that the sixteenth century made an important contribution to informal
logic is at best exaggerated.
CONCLUSION
To conclude this survey of changes in logic during the fifteenth and sixteenth
centuries, I shall attempt to isolate the main differences between medieval texts and
their post-medieval successors, whether commentaries on Aristotle or introductory
textbooks. One obvious difference is the emphasis on following the order and
material of Aristotle’s Organon. Such medieval material as survived was strictly
subordinated to this end, and even though Agricola and Ramus had tried to ignore
Aristotelian syllogistic and the doctrines propaedeutic to it, such as conversion and
opposition, their omissions were rapidly remedied by subsequent textbook writers.
Non-Aristotelian logic was on the whole to be excluded, but all of Aristotle himself
was to be retained. Fifteenth-century logic is still medieval, but sixteenth-century
logic becomes strictly Aristotelian.
However, there is a second difference to which I have so far paid little attention,
and which concerns the language used in logical writings. Medieval logicians
treated Latin as a technical, almost artificial language. They were deeply concerned
with the effects that different word-orders and the addition of extra logical
particles had on both meaning and reference, and they frequently tried to express
semantic differences through different syntactic structures. The clearest indication
of their attitude toward language is the place of sophismata in their logical texts,
for sophismata are precisely those tortured fragments of language which best illustrate
or raise logical problems; 163 and these logical problems are in turn solved
by means of the tools provided by supposition theory and those doctrines allied
to it. The language of a post-medieval logician, whether humanist or Aristotelian,
commentator or textbook writer, is totally different. Sophismata have completely
disappeared, and so too has any attempt to treat Latin as a technical language in
which different word-orders represent different logical structures. The propositions
used for such operations as syllogistic conversion are presented in an already fully
quia ita est: sed quia verisimile est in actione.”
162 Niphus, Dialectica ludicra, f. 111 rb.
163 For Juan Luis Vives’s attack on sophismata, which includes a wild variety of examples (many,
I think, invented by Vives) see Guerlac, Juan Luis Vives, passim.