Ilm al-Qiyas — Analogy in Islamic Law: The Fourth Source, Its Four Pillars, and the Ismaili Rejection of Individual Reasoning

The Four Pillars of Valid Qiyas

Every valid analogy requires four elements:

1. Al-Asl (the original case): the established Quran or Sunna ruling from which the analogy departs. Example: wine is prohibited (Quran 5:90).

2. Al-Far’ (the new case): the situation to which the ruling is being extended. Example: cannabis.

3. Al-‘Illa (the effective cause): the quality that connects the original ruling to the new case and justifies extending the ruling. Example: intoxication.

4. Al-Hukm (the ruling): what transfers from the original case to the new one. Example: prohibition.

The analogy succeeds if: (a) the ‘illa is correctly identified in the original case; (b) the ‘illa is present in the new case; (c) no other factor distinguishes the cases in a relevant way.

Al-Farq (Distinction)

The counter-move to qiyas: al-farq (distinguishing). A jurist who disagrees with an analogy demonstrates that a relevant difference exists between the original case and the new case — something that should prevent the ruling from extending. Valid farq invalidates the qiyas.

Schools on Qiyas

All four Sunni schools accept qiyas as the fourth source of law, though they differ on how broadly to deploy it:

• Hanafi: widest use of qiyas; developed istihsan (juristic preference) as an alternative when strict qiyas produces an unjust result
• Maliki: uses qiyas but prefers maslaha in some cases
• Shafi’i: codified qiyas systematically in Al-Risala — the first usul al-fiqh text
• Hanbali: most restrictive in deploying qiyas; prefers clear textual authority

Zahiri school: rejected qiyas entirely — only text, no analogy. Ibn Hazm was the Zahiri position’s greatest defender.

The Ismaili Rejection

In Ismaili jurisprudence, individual qiyas — where each jurist applies their own reasoning — is rejected as a source of law. Reasoning without the Imam produces divergent and unreliable results. The Imam is the living ‘illa, the living extension-principle: new questions go to the Imam (or to the Dai al-Mutlaq in the period of occultation) rather than to individual scholarly analogy.

See also: Ilm Al Usul, Ilm Al Hadith Types, Dai Al Mutlaq, Ismaili Dawat Organization, Nubuwwa Prophethood, Fiqh Al Taysir