Methodology: Textualism and the Rejection of Qiyas

Al-Ihkam fi Usul al-Ahkam by Ibn Hazm is the definitive systematic statement of Zahiri legal methodology, running to eight volumes in its complete form. It is simultaneously a positive exposition of the Zahiri approach and a sustained polemic against the juridical traditions that Ibn Hazm regarded as corruptions of genuine Islamic legal reasoning. Understanding the work requires grasping the fundamental Zahiri proposition: that Islamic law derives exclusively from the Quran, the authenticated Sunnah, and the explicit consensus of the Companions (ijma' al-sahabah), and that beyond these sources no human inference, however sophisticated, has binding legal authority.

The structural logic of Al-Ihkam follows from this position. The work begins with the epistemological foundations: how can we know what is obligatory, permissible, or prohibited? Ibn Hazm's answer is: only through the clear texts of revelation. He then proceeds systematically through the sources, analyzing the Quran with meticulous attention to its grammatical and lexical indicators and insisting that the outward (zahir) meaning of a text is binding unless another text explicitly qualifies it. His treatment of Sunnah is similarly rigorous in its insistence on textual evidence, but he accepts the authority of solitary (ahad) hadith in legal matters while developing stringent criteria for authentication.

The most distinctive and controversial section of the work is its comprehensive rejection of qiyas (analogical reasoning). Ibn Hazm argues that qiyas is, in principle, an act of legislating on behalf of God — attributing to the divine will a ruling that God has not explicitly communicated. He marshals Quranic verses and hadith to support this prohibition and then devotes extensive pages to dismantling the arguments offered in defense of qiyas by the four schools. He is particularly sharp in his criticism of the concept of the operative legal cause ('illa) — the feature of a case that is supposed to justify extending the ruling to analogous cases. This concept, he argues, is fundamentally indeterminate: jurists disagree endlessly about what the 'illa is, demonstrating that analogical reasoning produces not law but opinion.

The work also contains a detailed treatment of what Ibn Hazm considers legitimate forms of legal inference: inference from explicit general statements, from the structure of commands and prohibitions, from the silence of the texts. Within these boundaries, considerable legal analysis remains possible — but it is always anchored to textual evidence rather than floating on the reasoning of individual scholars.