An obligation, in the sense in which it was of interest to medieval logicians from about the early thirteenth century to the end of the scholastic period, is, according to Paul of Venice, a relation limiting one to take some statement affirmatively or negatively. This relation is based on the actions of two individuals: one (the opponent) obligates the other (the respondent) by first putting forward a sentence which the respondent agrees to affirm or deny for a limited time. The sentence the respondent agrees to affirm is called the positum; that which he agrees to deny, the depositum; and his act of agreeing, the admissio. After this relation is established between the opponent and respondent, the opponent proceeds by putting forward a series of sentences to which the respondent replies by granting, denying, or doubting — all in accordance with certain rules the two individuals have previously accepted as governing their exchange. If the respondent at any time grants what is inconsistent with the sentence he agreed to uphold, or responds in a way that violates the accepted rules, the exchange comes to an end. The respondent has failed in his obligation.