THE LOGIC OF AVICENNA BETWEEN AL-QIYĀS AND MANṬIQ AL-MAŠRIQIYYĪN

Avicenna's logic is presented in many treatises, of which the most important is Al-Qiyās (Prior analytics), which is included in his encyclopaedic book Al-Šifā’. But the treatise entitled Manṭiq al-mašriqiyyīn is said to express Avicenna's own logic by some commentators. One can thus ask: is this treatise in conflict with Al-Qiyās and the other logical writings? In this paper, we will answer this question by comparing Avicenna's analyses of the absolute – i. e. non modal – propositions. We will show that there is no radical difference between both treatises in this respect, since most conditions added to the absolute propositions in Al-Qiyās can be found in Manṭiq al-mašriqiyyīn. These conditions are: (1) “as long as S exists”, (2) “as long as it is S”, (3) “as long as it is P”, (4) “at some times”, (5) “at one determined time”, (6) “sometimes but not permanently”. In Manṭiq al-mašriqiyyīn, the ḍarūrīya contains (1), the lāzima contains (2), the muntašira contains (4), the mafrūḍa contains (5), the wujūdiyya contains (6), but (3) is abandoned. The waqtiyya was evoked in Al-Qiyās, although not classified. So the temporal analysis initiated in Al-Qiyās is pursued and developed in Manṭiq al-mašriqiyyīn, even if in the latter it is sometimes confused.