Handbook of the History of Logic: - Fordham University Faculty

The Development of Supposition Theory in the Later 12 th through 14 th Centuries 205
The second part of the theory states how supposition bears on truth
conditions. As stated in section 3.3, a sentence of the form:
Every A is/was/will be/can be B
is uniformly true iff the subject has supposition, and everything for
which the subject supposits is (tenselessly) something for which the
predicate supposits. Likewise:
Some A is not/was not/will not be/can not be B
is true iff either the subject lacks supposition, or it supposits for something
that the predicate does not supposit for.
Thus, although the past tense shows up on the copula ‘was’ in‘Every donkey was
running’, it has no effect on the verb at all; the verb represents tenseless identity
in every case. The tense only affects (ampliates or restricts) what the subject and
predicate terms supposit for. Likewise (apparently) for modal propositions: ‘every
donkey possibly runs’ is true iff every possible donkey is (tenselessly) a possible
runner. And ‘every chimera is conceivable’ is true iff every chimera — possible
or not — is (tenselessly) something able-to-be-conceived. (The term ‘conceivable’
does the ampliating here because it pertains to the soul.)
Restriction of a term by other terms
One topic that will not be discussed here is the restriction of a term by another
term or by a relative clause modifying it. All writers agree that in this proposition:
Every grey donkey is running
the complex term ‘grey donkey’ supposits only for donkeys that are grey, not for
donkeys in general, or for grey things in general. Contemporary logicians might
suppose that the simple term ‘donkey’, which is part of the complex subject,
supposits for all presently existing donkeys, and that the supposition of this simple
term is unaffected by its being modified. Some medieval writers however hold that
the modifier ‘grey’ restricts the supposition of the simple term ‘donkey’ so that it
only supposits for donkeys that are grey. 57 The complex term thus supposits for
exactly the things that the simple term ‘donkey’ supposits for in this context.
If this is so, it is not relevant to any of the truth conditions of sentences containing
such constructions. This is because it is the complex term ‘grey donkey’
that interacts with the rest of the proposition; ‘Some grey donkey is running’ is
true if and only if the subject (’grey donkey’) and predicate have a suppositum in
common. The complex term supposits exactly for donkeys that are grey, whether
‘donkey’ is restricted by ‘grey’ or not. In either case you take the grey things and
then intersect these with the donkeys — or with the donkeys that are grey; it
57 See Peter of Spain T XI.4. At XI.5 he also holds e.g. that in ‘grey donkey’ the‘donkey’
restricts ’grey’ to suppositing only for donkeys.