Handbook of the History of Logic: - Fordham University Faculty

536 Simo Knuuttila
modal terms. These were taken to have a categorematic meaning as de re modes
and a syncategorematic meaning as de dicto modes. 102
The distinction between various interpretations of possibility propositions was
extensively dealt with in twelfth- and thirteenth-century discussion of Aristotle’s
examples of fallacies based on shortcomings in distinguishing between compound
and divided meanings. The compound interpretation of ‘A standing man can sit’
was usually taken to be ‘It is possible that a man sits and stands at the same time’.
Many authors formulated the corresponding divided interpretation as involving a
reference to a later or earlier time. 103 The reference to another time was based on
the assumption that the necessity of the present prevents the acceptance of
(16) p (now) & ♦ − p (now).
The authors who regarded (16) as false did not operate with counterfactual alternatives.
They thought that if an unactualized present possibility is assumed to
be actualized, something impossible follows, as is seen in the rule of thirteenthcentury
obligations logic, according to which one should deny that the ‘now’ of a
disputation is the present ‘now’, if it is assumed for the case of argument that a
contingent proposition which is false now is true. 104
In discussing the proposition ‘That which is standing can sit’ the author of
the Dialectica Monacensis states that the de re possibility can be predicated of
the subject abstracting from the subject’s actual qualifications; this may imply a
counterfactual interpretation of the modal proposition. Another example of the
idea of modal alternativeness in this and some other works is found in the theory
that the word ‘can’ may ampliate the subject term so that it stands for actual and
merely possible beings. 105
102 For some examples, see Syncategoremata Monacensia in Braakhuis 1979, 99-100, translated
in N. Kretzmann and E. Stump (eds.), The Cambridge Translations of Medieval Philosophical
texts I: Logic and the Philosophy of Language (Cambridge: Cambridge University Press, 1988),
168-9; William of Sherwood, Syncategoremata, ed. J.R. O’Donnell, Mediaeval Studies 3 (1941),
72-3, trans. with an introduction and notes by N. Kretzmann in William of Sherwood’s Treatise
on Syncategorematic Words (Minneapolis: University of Minnesota Press, 1968), 100-101; Jacobi
1980, 86-7, 207-9, 339-41.
103 See notes 15 and 29 above.
104 In De obligationibus attributed to Willam of Sherwood, the author writes: ‘When a false
contingent proposition concerning the actual instant of time has been posited one must deny that
it is the actual instant. This is proved as follows. Let A be the name of the actual instant; it is
discrete name and not a common name. When it is false that you are in Rome, it is impossible
that it is true then or in A. It can become true only through a motion or through a change, but
it cannot become true trough a motion in A, because there is no motion in an instant. And it
cannot become true through a change, since if there were a change to truth in A, the truth would
be in A, for whenever there is a change, there is the term of that change. So it is impossible
that this false proposition becomes true in A. Therefore, if it is true, A is not actual.’ The text
is edited in R. Green, The Logical Treatise ‘De obligationibus’: An Introduction with Critical
Texts of William of Sherwood (?) and Walter Burley (PhD diss., University of Louvain, 1963).
105 de Rijk 1967, II-2, 570.18-571.9; 623.33-624.26. Cf. 1.5 above.