Handbook of the History of Logic: - Fordham University Faculty

The Development of Supposition Theory in the Later 12 th through 14 th Centuries 215
5.5 Ampliation due to Semantic Words
Semantic terminology ampliates terms, just as do words that pertain to the soul.
For example, ‘signify’ ampliates terms as widely as they can be ampliated. This
is clear from examples like ‘In any proposition, ‘Dodo’ signifies all dodos’, which
is intended to apply to all dodos, not just to presently existing ones. This is
consistent with no dodo presently existing. Some authors would accept ‘chimera’
signifies chimeras and no chimera is possible’. (Those who oppose this view do so
because they think that there are no chimeras at all to be signified.) The same
goes for ‘supposit’, as in ‘dodo’ supposits for dodos in past tense sentences’, etc.
One might want to ask about the ontological commitments of such a theory.
The logic and semantics alone don’t commit you to much. Saying that ‘donkey’
signifies all donkeys is, by itself, a truism. Since it is an affirmative sentence it
commits you to there being at least one donkey. But no more. It is possible to
state various commitments within the theory. For example, one might say ‘Some
donkey which will be grey is not [a being]’. This commits you to future donkeys
that do not exist. But only if you endorse it. If you thought that God had just
destroyed all donkeys, and would not permit there to be any more, you wouldn’t
assert that sentence. Likewise ‘Some donkey which was not and which is not and
which will not be is possible’ commits you to possible donkeys that are not actual
at any time; if you don’t believe in them, you needn’t endorse the proposition.
Some tried to argue like this: Since ‘chimera’ signifies all chimeras, every
chimera is signified by ‘chimera’. The conclusion is an affirmative sentence, which
seems to commit you to chimeras (perhaps impossible ones, since none are possible).
Buridan escaped this conclusion by denying that ‘chimera’ signifies all
chimeras. Since there are no chimeras, the word does not signify anything. This
does not make it meaningless, because “chimera” is a complex concept, which is
composed of concepts which are themselves non-empty and meaningful. indexampliation
and restriction—)
6 NON-EXTENSIONAL CONTEXTS
In contemporary semantics, non-extensional contexts have received a great deal of
attention. These are contexts in which interchanging expressions with the same
extension can change the truth-value or reference of the whole context. This section
covers three types of non-extensional constructions that were widely discussed
by medieval logicians.
6.1 Belief Contexts
That-clauses are paradigm non-extensional contexts. Other types of contexts are
equally non-extensional. In English, we have “accusative-infinitive” constructions
that behave somewhat like that-clauses. An example is the clause in the second
of these sentences: