 The extent to which hypothetical syllogisms are treated in Avicenna’s various logical works varies significantly. A great deal of material is left out of the abridged treatments (for instance in the Nağāt and in the Išārāt) compared to the extensive analysis provided in the Qiyās (and to that promised but never delivered—as far as we know—in the frequently announced Kitāb al-Lawāḥiq, the Book of the Appendices). The criteria of selection are not just pragmatic (hypothetical syllogisms are significantly more complex, if only in virtue of the compounding effect generated by an additional layer of quantification) but also based on the idea that some combinations are more natural (perhaps more intuitive) than others.