Uṣūl al-fiqh is not a list of rulings — it is the science that produces them. It settles which sources count as proof, how a text is read for its ruling, and how a jurist reasons from evidence to verdict. Change the method and the answer changes; this is why the madhāhib differ. What follows is the machinery. The rulings it yields — the masāʾil — live in Fiqh.

The four Sunnī schools agree on the Qurʾān, the Sunna, ijmāʿ and qiyās. They diverge on the disputed proofs below — and that divergence is the root of most khilāf.

Before a proof can be applied it must be read: is the wording a command or a recommendation, general or specific, literal or figurative? These principles of Arabic are where a single word decides a dispute. Each opens in the Arabic lens.