What is the difference between a legal principle (ḍābiṭ sharʿī) and a condition (sharṭ), and how do we distinguish between an Usuli (legal theory) and a Fiqhi (jurisprudential) rule?

The legal criterion (ḍābiṭ sharʿī): What is meant in Islamic law by a word or a command.

The condition (sharṭ): That which negates a ruling by its absence, but does not necessarily establish it by its presence. It has types: legal (sharʿī), intellectual (ʿaqlī), linguistic (lughawī), and customary (ʿādī).

The maxim (qāʿidah): Linguistically, that upon which something is based. Technically, a universal proposition applicable to its particulars, or a predominant ruling from which the ruling of specific juristic issues can be directly derived.

Usuli (foundational) maxims (al-qawāʿid al-uṣūliyyah): Definitive maxims derived from the inductive study of a body of evidence that converges on a single meaning, thereby establishing certainty in it.

Differences between Usuli and Fiqhi (juristic) maxims:

1. Usuli maxims are universal, encompassing all their particulars, whereas Fiqhi maxims are predominant.

2. Usuli maxims serve as evidence for legal rulings, whereas Fiqhi maxims are a collection of similar rulings for the purpose of simplifying issues.

3. Usuli maxims existed before the subsidiary issues (furūʿ), whereas Fiqhi maxims came into existence after the subsidiary issues.