Reason is a source too: 'Aql (reason) is the third source of Islamic law in Shia Usul. The key principle is Talazum: "Whatever reason decisively judges, the Shari'a also judges." Allah is perfectly just, so His law cannot command what pure reason clearly sees as unjust, or forbid what pure reason clearly sees as good.
Two kinds of reasoning: Reason works in two ways. Mustaqillat 'Aqliyya are independent rational judgments — for example, "Oppression is wrong" and "Gratitude to one who helped you is due." These are themselves rulings of the law. Malazima 'Aqliyya are rational implications — if Hajj is obligatory, then travelling to Makkah is also obligatory, because the duty cannot be done without it.
Consensus is a window, not a law-maker: Ijma' is the agreement of scholars. In Shia Usul it has no power on its own, because scholars are not infallible — many people agreeing does not by itself create law. Ijma' counts only when it is Kashif, a revealer of the opinion of the Imam (as). The scholars are witnesses to the Imam's (as) teaching, not legislators.
Some things are rejected: Reasoning by analogy (Qiyas), personal preference (Istihsan), and rulings based only on public interest (Masalih Mursala) are not accepted as sources. Custom ('Urf) is not a source either, though it helps us understand the meaning of words in old texts.
Example
A child takes another child's toy and breaks it on purpose. Even before reading any book, your reason says: that is wrong, and he should make it right. That judgment of reason — oppression is wrong — is itself part of Islamic law, because Allah is just and His law agrees with sound reason.
Key Terms
- Al-'Aql (العقل) — reason; the third source of Islamic law in Shia Usul
- Talazum (تلازم) — the principle that whatever reason decisively judges, the Shari'a also judges
- Ijma' (اجماع) — consensus of scholars; authoritative in Shia Usul only as a revealer (Kashif) of the Imam's (as) view
- Kashif (کاشف) — a revealer; what shows us the opinion of the Imam (as)
Quran or Hadith
Imam Musa al-Kadhim (as) said: "Allah has two proofs over mankind — an outward proof and an inward proof. The outward proof: the Prophets and the Imams (as). The inward proof: the 'Aql — reason." (Al-Kafi) — to be checked. This is why reason stands as an independent source beside revelation.
Fresh diagram to be drawn: Two lamps side by side — one labelled "Outward proof: Prophets and Imams (as)", one labelled "Inward proof: 'Aql (reason)" — both lighting the same path.
- 'Aql (reason) is an independent source of Islamic law.
- Talazum: whatever reason decisively judges, the Shari'a also judges.
- Ijma' counts only when it reveals the Imam's (as) view — scholars are witnesses, not legislators.
- Qiyas, Istihsan, and Masalih Mursala are not accepted as sources.