 The medieval logical genre of sophismata (see the entry on  sophismata  in this encyclopedia) appears especially relevant to obligations. A typical sophism in this sense consists of a case (casus), a sophisma sentence, arguments for and against the sophisma sentence based on the case, and a solution. The case is often imagined rather than real or even genuinely possible. One relatively natural way to think of a sophism would thus be to take the case (casus) as a positio in the sense of obligational disputations. Indeed, Richard Kilvington’s comments of the obligational rules in his Sophismata show him thinking that obligational rules regulate how one ought to evaluate sentences on the basis of the case (casus) in a sophisma. (See Kretzmann &amp; Kretzmann 1990a and 1990b.)