 The discussion of productive moods in the Qiyās and in the Nağāt follows the order and method of presentation of the Prior Analytics and focuses on different modal mixes (iḫtilāṭāt) that are then distinguished by figure (for example, the LX or the LM combinations in the first, second, and third figure). In the Išārāt Avicenna chooses a different approach and discusses productivity by figure, not by mix. This enables him to present more effectively a number of general principles governing inferences in each figure, and most importantly modifications to the so-called rule of the major for the first figure (Street forthcoming). The rule of the major tells us that the modality of the conclusion in first-figure syllogisms follows the modality of the major premise, except in two cases that will be discussed below (Ld1LL and XMM).  Given the logical priority ascribed by Avicenna to the first figure, this move represents a significant gain in terms of simplicity.