The Chapter on Analogy (Qiyas)

Linguistically, analogy (qiyas) is defined as comparison (between two things) and measurement (of two things). As for terminological definitions, we have (two specific types of analogy):

1) Co-presence²⁰ (qiyas al-tard) is the attachment of a judgment (hukm) governing a principal case (asl) to a derived case (far) due to the jurist’s deduction that both cases share the same occasioning factor (Illa) with respect to the judgment (hukm) in question.

2) Co-absence²¹ (qiyas al-'aks) is a type of reasoning whereby the converse of the judgment (hukm) of a principal case (asl) is applied to the derived case (far⁴), due to both cases having differing or opposing occasioning factors ('ilal). An example mentioned by Zaydi and Hanafi jurists is the case of fasting (sawm) during the vowed i'tikaf (al-i'tikaf bi-l-nadhr).²² Ritual prayer (salah) is not deemed a necessary condition for the validity of I'tikaf more generally because it has not been stipulated as such for the vowed i'tikaf. Extending this principal case (asl) of ritual prayer to the derived case (far') of fasting, the same occasion­ing factor ('illa) is not present. It has been determined that fasting is a necessary condition for the validity of the vowed i'tikaf.

3) If we were to combine both into one definition, we would say: the application of the same ruling or its converse, of the principal case, to the derived case, due to their sharing the same or having different occasioning factors.

In this short passage al-Wazir makes his views apparent on three issues. First, similar to the Sun­ni jurists he cites - and contrary to the Twelvers - he considers qiyas to be a valid juridical tool of interpretation. Second, the disagreement between the mukhattba - namely the Twelvers - and musawwiba - namely the Zaydis and majority of Hanafis, Malikis, and Shafi'is - on whether the judgment of every mujtahid is correct, versus the existence of only one empirically correct judg­ment in alignment with God’s Will, is a significant fissure in usul debates that will affect subse­quent conversations. Third, co-presence (qiyas al-tard) and co-absence (qiyas al-'aks) are both valid forms of analogical reasoning (qiyas). While they can be combined into one singular idea, they are sufficiently distinctive such that they are best treated as different sub-types of analogical reasoning (qiyas). The recognition of co-absence (qiyas al-'aks) was an enormously controversial issue among jurists, yielding extensive debate between those who favoured and opposed its va­lidity. Hence, as we will see, Ahmad b. 'Abdallah cites the two prominent Shafi'i jurists Abu Hamid al-Ghazali (d. 505/1111) and Abu l-Ma'ali al-Juwayni (d. 478/1085) in support of al-Wa- zir’s general position on qiyas. However, on the more specific matter of co-absence (qiyas al-'aks), al-Juwayni does not consider it be a valid form of analogical reasoning while al-Ghazali does.