Handbook of the History of Logic: - Fordham University Faculty

632 E. Jennifer Ashworth
sorites and dilemma, but he disapproved of them both; and the claim that he introduced
a new interest in sorites and other classical forms of argument is hardly
borne out by the evidence. It is true that some later authors mention sorites, but
in the hands of Philip Melanchthon and Petrus Fonseca it is identified with the
medieval argument ‘From First to Last’, a linked chain of syllogisms (or conditionals).
114 In his latest logical work, Erotemata dialectices, Melanchthon explains
that the chain is based on movement from lowest species to highest genus, or
from causes to proximate effects. 115 Dilemma does not fare better. Both Jodocus
Clichtoveus and Domingo de Soto give lengthy accounts of the lawsuit between
Protagoras and Euathlus, as reported by Aulus Gellius, but they assimilate the
story to medieval discussions of promises that cannot be kept. 116 Agostino Nifo
in his Dialectica ludicra has a section entitled De dilematibus et antistrephontibus:
idest de insolubilibus, but places the classical material in the context of medieval
discussions of semantic and pragmatic paradoxes. 117 Two further points casting
doubt on Jardine’s account of Valla’s importance are first, that the evidence is
against his having been a sceptic; 118 and second, that the work had only a limited
manuscript circulation, and few printed editions. 119
While Valla seems not to have played the role assigned to him by Jardine, we
still need to confront the wider questions of how far logic was rhetoricized, and
how far humanist dialectic, or any other type of sixteenth-century logic, was concerned
with probabilistic and informal argumentation. In order to do this, we
need to make a series of distinctions about the key terms, ‘dialectic’, ‘probability’,
‘rhetoric’, and ‘informal’, as a lack of such distinctions in the literature has
obscured the points at issue.
2 DIALECTIC AND PROBABILITY
In order to understand the issues here we need to consider the background. The
Aristotelian syllogism was taken to be the most important form of argumentation,
114Melanchthon, Compendiaria dialectices, cols. 747–748, has a discussion of sorites after the
other four forms of argumentation. He also mentions (col. 748) other arguments such as the
Crocodile, Asystaton, and Antistrephon, but only to say that they can be omitted. For Fonseca
on sorites, seeInstituições Dialécticas, p. 348.
115Melanchthon, Erotemata dialectices, cols. 624–626.
116Jodocus Clichtoveus, Jacobi Fabri Stapulensis artificiales introductiones per Judocum Clichtoveum
in unum diligenter collecte (Parisiis, 1520), f. 139 v–140r; Domingo de Soto, Summulae,
f. lv rb–va. For the problem of promises that cannot be kept, see E. J. Ashworth, “Will Socrates
Cross the Bridge? A Problem in Medieval Logic”, Franciscan Studies 36 (1976), 75–84, reprinted
as Study XII in Ashworth, Studies in Post-Medieval Semantics. For a full discussion of the limited
treatment of dilemma and other classical arguments in sixteenth century logic, see Gabriel
Nuchelmans, Dilemmatic Arguments: Towards a history of their logic and rhetoric (Amsterdam:
North-Holland, 1991).
117Augustinus Niphus, Dialectica ludicra (Venetiis, 1521), f. 156 ra– f. 163 ra.
118See John Monfasani, “Lorenzo Valla and Rudolph Agricola,” Journal of the History of Philosophy
28 (1990), 181–200.
119Mack, Renaissance Argument, p. 115.