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INTRODUCTION TO JEAN BURIDAN’S LOGIC
solution. In the latter case in which we descend first under the predicate-
term, a crucial step in the argument was that ‘some man’ in each conjunct
be taken not referentially, but attributively. Thus each occurrence of ‘some
man’ in “some man is not this Greek and some man is not that Greek”
should be read as ‘some man or other (indifferently).’ Yet this is to assign
non-distributive confused supposition to the subject-term; in the example,
the subject-term was said to have determinate supposition. To put the
point a different way: if the subject-term has determinate supposition then
an equivalent descent can only be made taking the subject-term thus cor-
responds to a ‘priority of analysis’ rule, and the so-called ‘problem’ of the
O-form is resolved.
6.8 Ampliation: Time and Modality
Natural supposition, as we have seen, ampliates a term to stand for
all of the items it signifies, whether past, present, or future (Rule Amp-5 in
TS 6.2.1). Accidental personal supposition, though, may be concerned with
the actual or the possible, with the present or past or future. Buridan, like
most mediæval logicians, takes tensed sentences to be complete: they are
not to be replaced by tenseless sentences with a time-index, or expanded to a
canonical form; their truth-value can be assessed immediately. Now personal
supposition as described above strictly applies to present-time assertoric
discourse; the extension theory of ampliation (TS 6.1.1): a term is said to
be ampliated if the scope of its reference is widened, made more “ample”
(TC 1.6.4). Naturally, this suggests that ampliation is possible only for
terms which are able to be predicated of many, that is, terms which are
semantically general; singular referring expressions cannot be ampliated and
remain singular. This is what Buridan maintains: in Soph. 5 Sophism 3
he asserts that discrete terms cannot be ampliated. Hence the theory of
ampliation will deal only with common terms.
Buridan suggests in TS 3.4.8–10 that the copula of a Mental sentence
is timeless, but whether this is so will not make any appreciable difference
to his theory; he still has to explain sentences about times other than the
present. Buridan admits two forms of temporal ampliation: (i ) the cop-
ula itself is modified, either adverbially or by tensing the verb; (ii ) certain
terms in themselves imply a difference of time. In either case a term is am-
pliated from its original status (TS 6.2.1), which is the present supposition
it possesses.
Let us begin with the case in which the copula is tensed; by TC 1.6.3
we know that a term retains its supposition for present items, and so Buri-
dan offers the following paradigms for tensed sentences:
• “S was P”: What was or is S was P [rule Amp-1 in TS 6.2.1;
c Peter King, from Jean Buridan’s Logic (Dordrecht: D. Reidel 1985) 3–82.
INTRODUCTION TO JEAN BURIDAN’S LOGIC
49
TC 1.6.4].
• “S will-be P”: What is or will-be S will-be P [Rule Amp-2 in TS 6.2.1;
TC 1.6.4].
The supposition of the subject is thus ampliated to include past or future
existents as well as present existents, analyzed as a hypothetical sentence
with a disjunctive subject. This sentence is not equivalent to a disjunction
of two sentences.
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These paradigms have the peculiar consequence that
“An old man will be a young man” may be true: this sentence is equivalent
to “What is or will be an old man will be a young man,” and this sentence
may be true of a bouncing baby boy, who will eventually be an old man, will
(first) be a young man (Soph. 4 Sophism 4). On the other hand, Buridan’s
analysis avoids nasty ontological puzzles; there is no way to move from the
sentences “There was a statue” and “That statue no longer exists” to the
conclusion “there is a statue which does not exist.” However, a version of
the “what is. . . ” locution can temporally fix the extension of the subject-
term: the subject-term of “What was S was/is/will-be P ” refers only to
present existents, of “What will-be S was/is/will-be P ” refers only to future
existents.
The predicate-term of sentences in which the copula is tensed is
carried along to supposit for items at the time of the verb, provided that
the term itself does not imply a different time (TC 1.6.1 and 1.6.20). Thus
in a sentence of the form “S will be P ” the subject-term is ampliated to
supposit for what is or will be S, while the predicate-term supposits for
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Buridan argues for this point in TC 2.4.1–7. The nonequivalence mentioned is es-
tablished for tensed sentences and for modal sentences. Buridan’s argument proceeds
as follows: consider the sentence (S*) “What is B can not-be A or what can be B
can not-be A”—an equivalence Buridan will deny. He argues that when there are no
actual B, the first disjunct of (S*), ‘What is B can not-be A,’ will be true, since it
is a negative sentence with an empty subject-term. (Equally “Unicorns do not have
wings” is true for the same reason.) Since one of the disjuncts of (S*) is true, (S*) is
true. Buridan now claims that (S), however, may be false while (S*) is true, clearly
showing the nonequivalence of (S) and (S*). He suggests that (S) would be false for
the case of a possible (but non-actual) B that must be A, that is, cannot not-be A.
Since (S) ampliates its subject to stand for possibles, (S) would be false. An example
will help. Suppose that God destroys the human race, and consider the sentence (S)
“A man can not-be rational.” The proposed equivalent (S*) “What is a man can
not-be rational or what can be a man can not-be rational” will be true, since its first
disjunct is a negative sentence with an empty subject-term. But it is part of the
nature of man to be rational; it is part of the human essence. Thus any possible man
must be rational, that is cannot not-be rational, and so (S) is false while (S*) is true.
Buridan opts for understanding (S) by the equivalence (S**) “What is or can be B
can not-be A,” whose truth-conditions are the same as those for (S).
c Peter King, from Jean Buridan’s Logic (Dordrecht: D. Reidel 1985) 3–82.