Supposition Theory - Modes of Supposition

Modes of Supposition

Personal Supposition was further divided in types such as discrete, determinate, merely confused, and confused and distributive. In 1966 T.K. Scott proposed giving a separate name for Medieval discussions of the subvarieties of personal supposition, because he thought it was a fairly distinct issue from the other varieties of supposition. He proposed calling the subvarieties of personal supposition a theory of "modes of supposition."

The Medieval logicians give elaborate sets of syntactical rules for determining when a term supposits discretely, determinately, confusedly, or confusedly and distributively. So for example the subject of a negative claim, or indefinite one supposits determinately, but the subject of a singular claim supposits discretely, while the subject of an affirmative claim supposits confusedly and determinately. Albert of Saxony gives 15 rules for determining which type of personal supposition a term is using. Further the medieval logicians did not seem to dispute about the details of the syntactic rules for determining type of personal supposition. These rules seem to be important because they were linked to theories of descent to particulars and ascent from particulars.

When I say I want to buy a cup I've made an indefinite affirmative claim, with cup as the predicate term. Further cup is a common term, including many particular cups within it. So if I "descend to particulars" I can re-phrase my claim as I want to buy this cup or I want to buy that cup, or I want to buy that other cup - and so on for all cups. If I had an infinite disjunction of all particular cups, it could stand in for the term cup, in its simple supposition in I want to buy a cup. This is called determinate supposition. That is when I say I want to buy a cup I mean some determinate cup, but I don't necessarily know which one yet. Likewise if I say Some cup isn't a table, I could substitute This cup isn't a table, or that cup isn't a table or ...

On the other hand if I say No cup is a table, I don't mean This cup isn't a table or that one isn't a table or ... I mean This cup isn't a table, AND that cup isn't a table, AND that other cup isn't a table, AND .... Here I am referring not to a determinate particular cup, but to all cups "fused" together, that is all cups "confusedly." This is called confused and distributive supposition.

If I say This cup is made of gold I cannot descend to a disjunction of particulars, or to a conjunction of particulars, but only because this cup is already a particular. This kind of personal supposition is called discrete supposition.

However, the predicate of a universal affirmative claim won't really fit any of these models. All coffee cups are cups does not imply All coffee cups are this cup, or all coffee cups are that cup, or ..., but still less does it imply All coffee cups are this cup, and all coffee cups are that cup, and .... On the other hand, if it happened to be the case that there was only one coffee cup left in the world, it would be true that All coffee cups are that cup, so I can validly infer from All coffee cups are that cup, to All coffee cups are cups. Here descent to disjunction fails, and descent to conjunction fails, but "ascent from particulars" is valid. This is called "merely confused supposition."

That is basically how the theory works, a much thornier problem is exactly what the theory is for. Some commentators, like Michael Loux, have suggested that the theory of ascent and descent to particulars is intended to provide truth conditions for the quantifiers. T. K. Scott has suggested that the theory of supposition proper was designed to answer the question What kind of thing are you talking about? but the theory of personal supposition was aimed at answering the question How many of them are you talking about? Paul Spade has suggested that by the 14th century the theory of modes of personal supposition wasn't aimed at anything at all anymore.