Handbook of the History of Logic: - Fordham University Faculty

562 Simo Knuuttila
probabilism and probabiliorism. Thomas Aquinas, Boethius of Dacia, and some
other Parisian masters explained Aristotelian dialectical probabilities by stating
that what is probable in the sense that most experts accept it is probably true
because it is not probable that the majority of well informed experts would be
mistaken in the same way. 224 These and other similar examples show that, contrary
to what has been sometimes maintained, an intuitive conception of objective
frequency probability, different from epistemic probability, was developed in the
Middle Ages. 225
The question of the relationship between epistemic propositions de dicto and de
re belonged to standard fourteenth-century topics of epistemology. It was thought
that knowledge statements de dicto did not imply knowledge statements de re or
vice versa. 226 Buridan says, however, that when a person knows that some A is B,
then of something which is A he or she knows that it is B. The reason for denying
this could be that Socrates does not know which A is B. Buridan would agree that
in this sense the de re reading does not follow from the de dicto reading, but there
is another kind of de re reading (or which might be called so) which does follow
from the de dicto reading. This is a kind of intermediate reading between pure
de dicto and de re readings. The idea can be formulated as follows. According to
Buridan, statements of the type
(22) Ks(Ex)(Fx)
imply that there are individuals having property F , although S does not necessarily
know which they are. In principle they are identifiable, however, and if we suppose
that one of them is z, we can write:
(23) Ks(Ex)(Fx) → (Ex)((x = z) &Ks(Fx)).
From the de dicto statement ‘Socrates, who is sitting in a cellar, knows that a star
is above’ it does not follow the de re reading understood as ‘There is a star which
Socrates knows as the star which is above’, but the following de re reading does
follow from it: ‘There is a star of which Socrates knows that it is above, although
Socrates does not know which star it is.’ 227
Buridan was not the first to employ this reading. In his De obligationibus,
Walter Burley discussed the following case:
224 See Thomas Aquinas, Summa theologiae II-1.105.2, ad 8; II-2.70.2; Boethius of Dacia, Quaestiones
super librum Topicorum, ed. N. G. Green-Pedersen and J. Pinborg, Corpus Philosophorum
Danicorum Medii Aevi VI.1 (Copenhagen: Gad, 1976), III.14, 187.
225 For this notion of probability and its role in later medieval thought, see I. Kantola, Probability
and Moral Uncertainty in Late Medieval and Early Modern Times (Helsinki: Luther-Agricola
Society, 1994); for later discussions , see S.K. Knebel, Wille, Würfel und Wahrscheinlichkeit. Das
System der moralischen Notwendigkeit in der Jesuitenscholastik 1550-1700 (Hamburg: Meiner,
2000).
226 See, for example, the extensive discussion of the question in the second chapter of William of
Heytesbury’s Rules for Solving Sophismata (Venice 1494), translated in Kretzmann and Stump
1988, 436-72.
227 Sophismata, ed. T.K. Scott (Stuttgart-Bad Canstatt: Frommann-Holzboog, 1977) IV,14,
trans. by G. Klima in Summulae de dialectica, 900-902.