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Handbook of the History of Logic: - Fordham University Faculty

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The Development <strong>of</strong> Supposition Theory in <strong>the</strong> Later 12 th through 14 th Centuries 211<br />

is true iff Socrates at some time in <strong>the</strong> past thought a mental proposition whose<br />

content was that <strong>of</strong>:<br />

Euthyphro is a fool<br />

The interaction <strong>of</strong> tenses in main and subordinate clauses is not well understood.<br />

There is some hope <strong>of</strong> <strong>the</strong> medieval account doing as well in capturing <strong>the</strong> semantics<br />

<strong>of</strong> sentences with embedded subclauses as most modern <strong>the</strong>ories. However, this<br />

topic was not discussed in detail by medieval writers.<br />

5.3 Modal Propositions<br />

5.3.1 What are modal propositions?<br />

Buridan [SD 1.8.2 (67-70)] discusses three kinds <strong>of</strong> propositions that o<strong>the</strong>r writers<br />

call “modal”. He considers only one <strong>of</strong> <strong>the</strong>m to be genuinely modal.<br />

Kind 1: Non-modal Propositions containing Modal Words<br />

Some ordinary propositions contain modal words as parts <strong>of</strong> <strong>the</strong>ir subjects or<br />

predicates. Some examples are:<br />

A proposition is possible<br />

No proposition is necessary<br />

Some necessary proposition is false<br />

These are not modal propositions, even though <strong>the</strong>y contain modal words. In<br />

each <strong>of</strong> <strong>the</strong>se cases, <strong>the</strong> modal word is all or part <strong>of</strong> <strong>the</strong> subject or predicate, and<br />

thus does not affect <strong>the</strong> copula. A genuinely modal proposition is one in which<br />

<strong>the</strong> copula changes its mode. If nothing affects <strong>the</strong> copula, <strong>the</strong> proposition is<br />

by definition not modal. Buridan calls <strong>the</strong> displayed propositions “assertoric”.<br />

They require nothing special in terms <strong>of</strong> <strong>the</strong>ir syntax or <strong>the</strong>ir semantics. They<br />

just happen to quantify over propositions and contain terms that attribute modal<br />

properties.<br />

Kind 2: Composite Modal Propositions<br />

These are cases in which a modal word applies to an entire proposition. There<br />

are two kinds <strong>of</strong> such cases. In one kind <strong>of</strong> case, a modal adverb or prepositional<br />

phrase is used with scope over <strong>the</strong> entire sentence, such as:<br />

Necessarily every donkey is an animal<br />

Possibly, some donkey is grey<br />

In <strong>the</strong> o<strong>the</strong>r kind <strong>of</strong> case, a modal adjective or related word is applied to a whole<br />

embedded clause, such as<br />

That every donkey is an animal is necessary<br />

For some donkey to be grey is possible

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