Hypothetical-categorical syllogisms (qiyāsāt shartiyya-ḥamliyya) are among the most important topics in Ibn Sīnā’s hypothetical logic, and a substantial part of his analyses of hypothetical syllogisms in al-Shifāʾ is devoted to these syllogisms. This article examines the validity of some of these syllogisms on the basis of the interpretation of the categorical propositions employed in them. Given the view of some contemporary scholars that the propositions used by Ibn Sīnā are of the type of ḥaqīqiyya propositions, the question arises as to what effect considering categorical propositions as ḥaqīqiyya has on the assessment of the validity of these syllogisms.

To answer this question, the relation between the division of propositions into ḥaqīqiyya, khārijiyya, and dhihniyya and Ibn Sīnā’s logic is first examined, and the difference between universal and particular ḥaqīqiyya propositions is clarified. Then, some hypothetical-categorical syllogisms in al-Shifāʾ whose premises include a particular categorical proposition are analyzed. By presenting formal counterexamples and counterexamples based on concrete cases, it is shown that some of these syllogisms are not valid. The analysis further demonstrates that considering the particular categorical premise as ḥaqīqiyya cannot by itself guarantee the validity of these syllogisms, since the fact that a particular categorical proposition is ḥaqīqiyya does not entail that it is true in all the conditions, circumstances, and times relevant to the hypothetical proposition. Therefore, the assumption that the categorical propositions are ḥaqīqiyya cannot, by itself, provide an answer to the counterexamples presented in this article. Accordingly, considering particular categorical propositions as ḥaqīqiyya, without a qualification concerning their conditions of truth, is not sufficient to defend the validity of this group of syllogisms.