Handbook of the History of Logic: - Fordham University Faculty

The Development of Supposition Theory in the Later 12 th through 14 th Centuries 249
This donkey which is not an animal is not living and that donkey which
is not an animal is not living, and ...and so on for all the donkeys
that are not animals.
Then if the original were true, the conjunction would be true (and no ascent would
be possible). So this device seems to work fine (though it is not completely clear
how to spell it out).
8.3 Mobility
In the earlier theory some distribution was mobile, and some immobile. Mobility
most often referred to the possibility of inferring from a proposition the result of
replacing a common term with any singular term that supposits for one of the
things the common term supposits for. On the new theory, this describes the
descent condition that is part of the definition of distributive supposition. As a
result, mobility collapses into distribution, and there is no room for an immobile
distributed term.
This seems to be how Buridan viewed the matter. He does not talk about a
distributed term not being mobile. And in at least one place he seems to equate
the two notions. For example, in discussion of the effect of infinitizing negation
on a term, he says that a term is not distributed because it is not mobile: 103
Marsilius of Ingham also rejects immobile distributive supposition:
I answer that each term standing confusedly distributively has mobile
supposition. And I do not think the term man in this proposition
every man runs except Sortes to have immobile supposition, because,
in my opinion, this term stands for all men other than Sortes because
of restriction. 104
However, the notion of immobile distributive supposition was firmly established in
the tradition, and others sought to preserve it. Ockham, as quoted two sections
103 Buridan SD 4.3.7.3 (271): “ But concerning ‘Every non-man runs’ we should say similarly
that the term ‘non-man’ is distributed, while ‘man’ is no longer distributed, for reason of the
traditionally posited rule: ‘whatever mobilizes the immobilized immobilizes the mobilized, that
is, that which has the power to distribute an undistributed term removes the distribution of a
distributed one.”
The point here is that the prefix ‘non-’ by itself would distribute ‘man’, but so would the sign
‘every’. The second distribution removes the first, since the first mobilizes the supposition of
‘man’ and the second then immobilizes it. (Distribution of terms modified by ‘non-’ is discussed
later in this section.) Paul of Venice LP II.5 (153) makes a similar equation: “. . . according
to one rule pertinent to this matter, viz., whatever mobilizes the immobile, immobilizes the
mobile. That is: If any sign having the power to distribute some term finds again the same term
undistributed, the sign makes the term stand distributively; and if the sign finds again the same
term distributed, the sign makes the term stand without distribution, ...”
104 Marsilius (63) in [Bos, 1983]. The point seems to be that descent is possible under the term
‘man . . . except Sortes’ to every one of the things that it supposits for, namely, for every man
other than Sortes. (’Sortes’ is a common abbreviation of ‘Socrates’.) Also Marsilius TPT 1 (63)
“each term standing confusedly distributively has mobile supposition.”