 According to Walter Burley’s presentation of the obligational theory in the species of positio, the respondent faces a sequence of propositions that he must either grant or deny, one by one. The sequence starts with a positum that is normally a false sentence which the respondent has to grant. Then the following propositions are evaluated in accordance with what Burley calls the essential rules of obligations. Three of these rules can be found from practically all medieval discussions of the technique. According to them, the positum must be granted if it is put forward, anything following from the positum must be granted, and anything incompatible with the positum must be denied. (Cf. Green 1963, Kretzmann and Stump 1988. Modern discussions of Burley’s rules can be found in e.g., Ashworth 1981; Keffer 2001; Spade 1982; Spade and Stump 1983; Stump 1985; Yrjönsuuri 1994 and 2001.)