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INTRODUCTION TO JEAN BURIDAN’S LOGIC
5.5 Truth and Sentential Signification
What are the truth-conditions for categorical sentences? Buridan
investigates this question in Soph. 1–2, TC 1.102, and QM 6.8. He begins
by citing the standard definition of truth: “ A (categorical) sentence is
true if howsoever it signifies so it is (qualitercumque significat ita est ).”
To understand the definition we need the notion of the signification of a
sentence. Buridan considers and rejects four possible answers.
First, let us suppose that the definition refers to the immediate sig-
nification of all of its terms. But then we have the unfortunate conclusion
that every Spoken sentence is true, because its immediate significate is the
Mental sentence, which does exist (Soph. 1 Sophism 1); indeed, an inscrip-
tion or utterance is only a sentence in virtue of the corresponding Mental
sentence. The definition cannot mean the immediate signification of the
terms.
Second,
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suppose the definition concerns the ultimate signification,
of the terms in the sentence.
Since Syncategoremata by definition lack
ultimate signification, they are excluded. Yet this will have two unfortunate
results. First, a sentence and its contradictory may differ only in their
syncategoremata, as do “Socrates is a sexist” and “Socrates is not a sexist”;
they ultimately signify the same. Hence the proposed definition of truth will
not assign opposite truth-values to a sentence and its contradictory, which
is absurd. Second, by the Additive Principle, the ultimate signification of a
sentence such as “A man is an ass” is the sum of the ultimate significations
of its categorematic parts, namely men and asses. But there surely are men,
and there surely are asses; does this mean that the sentence “A man is an
ass” is true?
Third, several philosophers though the significate of a sentence was
an abstract entity called a complexe significabile, rather similar to the mod-
ern notion of a proposition. Buridan rejects this view for a variety of reasons:
(i ) even proponents of the complexe significabile, such as Gregory of Rimini
and Adam Wodeham, admitted that it was not to be found in any of the
Aristotelian categories; Buridan draws from this the conclusion that it is
nothing, and it is impossible to see how a sentence is true or false in virtue
of what is nothing at all. Yet (ii ) suppose it were not nothing, but some-
thing; then it either exists or fails to exist, and presumably in the former
case the sentence which signifies it is true and in the latter case the sentence
is false. But then one is maintaining that a false sentence literally has no
signification, which seems absurd: such sentences are false, not meaningless.
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For the next series of arguments see QPA 1.5 and QM 6.8.
c Peter King, from Jean Buridan’s Logic (Dordrecht: D. Reidel 1985) 3–82.
INTRODUCTION TO JEAN BURIDAN’S LOGIC
31
Finally, (iii ) suppose an existent complexe significabile is the significate of
true or of false sentences in some fashion. But suppose things changed in
the world. The abstract entity which is the complexe significabile is un-
changed, not being part of the world. But then a sentence is true or false
not in virtue of the world at all, which seems obviously ridiculous. Hence
the complexe significabile is not sufficient to account for truth-value.
Fourth, suppose that the significate of a sentence is the true or the
false, in the Fregean manner. But then the proposed definition is both
circular and uninformative.
The problem with all of these suggestions, Buridan thinks, is that
they fail to notice that sentences are far more than the terms which compose
them; they are the way in which we talk about the world. Buridan modifies
the proposed definition by adding a single clause:
A categorical sentences is true if and only if howsoever it signifies
so it is, in the thing(s) signified.
To understand what is ‘in’ the thing(s) signified we must move beyond the
simple signification of terms: we have introduced the notion of reference,
which for Buridan is part of the theory of supposition. Hence we need to
understand the nature of supposition before we can account for the truth
or falsity of sentences.
6. The Theory of Supposition
6.1 Supposition and the Theory of Reference
Supposition is a semantic relation, holding between term(s) and
things(s). The relation of signification, however, is also a relation of term(s)
and thing(s). Yet it is one matter to assign certain terms to certain things,
so that a language may be set up in the first place; this is the contribution
of signification. It is quite another matter to actually use that language to
talk about things; this is explained by supposition, which accounts for the
referential use of (significative) terms. Hence there are two major differ-
ences between supposition and signification: first, terms have signification
wherever they are found, inside or outside a sentence, but it is only in a
sentence that we use terms referentially, that is, actually talk about things
and say something about them. Therefore:
(1) A term has supposition only in a sentential context.
Second, we do not always use terms to talk about what those terms signify;
we use them in other ways as well. therefore:
(2) The kind of supposition a term has depends on its sentential context.
These principles govern the theory of supposition, and provide a context for
c Peter King, from Jean Buridan’s Logic (Dordrecht: D. Reidel 1985) 3–82.