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Qiyas — Analogical Reasoning in Islamic Jurisprudence: The Fourth Root of Fiqh

القِيَاس — القِيَاسُ فِي الفِقهِ الإِسلَامِيّ: الأَصلُ الرَّابِعُ لِلفِقه
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Qiyas (القِيَاس — analogy, analogical reasoning; from *qasa* — to measure, to compare; to apply a known standard to a new case by measuring them against each other) is the fourth root of Islamic jurisprudence after the Quran, Sunnah, and ijma. It is the method by which jurists extend the rulings of existing texts to new situations not explicitly addressed: when a new case shares the same legally effective cause ('illa) as an existing ruling, the existing ruling is applied to the new case. The Prophet (SAW) is reported to have approved of its use: when Mu'adh ibn Jabal was sent to Yemen, the Prophet asked him what he would do if he found no ruling in the Quran or Sunnah — Mu'adh said: 'I will use my own judgment (*ijtihad*).' The Prophet reportedly smiled and said: 'Praise be to Allah who has guided the messenger of His Prophet to what pleases His Prophet.' This article covers the four components of qiyas, the conditions for valid analogy, the types of 'illa and how they are identified, famous historical examples, and the Ismaili alternative to qiyas through living Imamic authority.

The Four Components of Qiyas

A valid qiyas requires four elements:

1. Al-Asl — The Original Case

The case for which the Quran or Sunnah has already established a ruling. This is the “source” from which the analogy draws.

Example: The Quran prohibits wine (khamr) — the asl.

2. Al-Far’ — The New Case

The new situation to which the ruling is being extended. The far’ must not have a direct textual ruling of its own (otherwise there is no need for qiyas).

Example: A new type of intoxicating beverage not known in 7th-century Arabia — the far’.

3. Al-‘Illa — The Effective Cause

The legally relevant reason (ratio legis) that explains why the ruling of the asl exists. The ‘illa must be: (a) legally relevant, (b) identifiable and constant, (c) present in both the asl and the far’.

Example: The ‘illa of the prohibition of khamr is al-iskaar — the capacity to intoxicate. The Quran prohibits khamr because it intoxicates; intoxication impairs the mind, which the maqasid protects.

The ruling of the asl that is extended to the far’. If the ‘illa is confirmed in the far’, the same hukm applies.

Conclusion: Any substance that intoxicates (al-iskaar) is prohibited, because the ‘illa (intoxication) is present. All intoxicating beverages are thus prohibited by qiyas on khamr.


How the ‘Illa Is Identified

Classical scholars developed multiple methods for identifying the ‘illa:


Types of Qiyas


The Ismaili Alternative

The Ismaili tradition accepts qiyas as a tool of zahir fiqh but maintains that it is inherently limited: human jurists, however skilled, can misidentify the ‘illa or apply it incorrectly. For questions of ta’wil (esoteric interpretation) and matters touching the batin of the Sharia, human analogy is insufficient — the living Imam’s authority (nass) is required because his knowledge is divinely guided rather than deduced. See [[tawil-esoteric-interpretation]] and [[ijtihad]].

See also: Shariah Sources, Fiqh Overview, Fiqh Madhabs, Ijtihad, Maqasid Al Shariah, Ijma, Tawil Esoteric Interpretation

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