Handbook of the History of Logic: - Fordham University Faculty

224 Terence Parsons
that result due to a term’s moving from one mode to another, producing a kind
of quantificational ambiguity. An example is the following inference:
Every man sees a donkey
∴ A donkey every man sees (= “for some donkey, every man sees it”)
In the premise, the term ‘donkey’ has merely confused supposition, and in the
conclusion it has determinate supposition. The error was identified as the fallacy
of moving from a term with merely confused supposition to one with determinate
supposition. 77 We would identify the error as involving a change in quantifier
scope. Modes of supposition are properties that are affected by the relative scopes
of quantifier words in the proposition. The mode of supposition of a term was as
important to medieval theorists as quantifier scope is to us today.
The modes of common personal supposition are also used in formulating rules
of inference that cover inferences that go beyond those addressed in the theories
inherited from Aristotle. (See sections 7.6 and 8.7.)
Once the importance of modes of supposition for inference was recognized, they
tended to become a topic of independent study.
7.1.3 Terms functioning as Denoting Phrases
One thing common to all parts of the tradition is that the modes are used to classify
terms, as opposed to denoting phrases that contain the terms. For example, in
‘Every donkey is running’ one classifies ‘donkey’ as having distributive supposition,
not ‘every donkey’. But the classification of terms is a classification of terms as
affected by quantifier signs. In the proposition ‘Every donkey is running’ the
classification of ‘donkey’ is sensitive to the ‘every’ preceding it. In most cases
it turns out that there is no significant difference between classifying denoting
phrases such as ‘every donkey’ or classifying main terms, such as ‘donkey’. So
when we classify ‘animal’ in‘Every donkey is some animal’ as merely confused,
we can, if we wish, see this as a roundabout way of classifying ‘some donkey’ as
merely confused in that proposition. (The classification of terms that are not the
main term of a denoting phrase needs additional discussion.) 78
77 In many cases, confusing one mode of supposition for another was seen as an instance of the
Aristotelian fallacy of form of expression. Peter of Spain T VI.8 (71) says: “ In the examples
above, ... the term ‘man’ stands for every man, running or not, but it makes the utterance true
for one man running. That each is determinate is clear, because in Socrates is an animal, Plato
is an animal, Cicero is an animal, etc.; therefore every man is an animal, there is a fallacy of
form of expression, shifting from many determinates to a single one.” A change is made in the
mode of supposition, but this is concealed because the words used before and after the change
seem to have the same forms. (The Latin that is translated here as “form of expression” is
‘figura dictiones’. This is often translated as “figure of speech”, but it does not involve any
figure of speech as this term is understood today.) The order of the words changes, but there
is no grammatical change, such as switching the subject and direct object, as in the fallacy of
amphiboly, or of grouping, as in the fallacy of composition or division.
78 Examples of terms that are not the main term of a denoting phrase are ‘donkey’ in‘Every
non-donkey is a stone’, and in ‘Every grey donkey is running’. These are cases in which the term
forms only part of a complex term that combines as a whole with a quantifier sign. Although