qiyas

Qiyas (Arabic: القياس) means analogy. In Islamic jurisprudence, it is a method of deriving legal rulings for new situations by applying a ruling from a known case to a different case that shares the same underlying cause ('illat). It is commonly regarded as a primary tool for extending the law in Sunni legal thought, after the Qur'an, the Sunna, and ijma' (consensus).

The process involves identifying the text that prescribes a ruling for a known case, determining the underlying reason or effect that justified that ruling ('illat), and then verifying that the new case shares the same 'illat. If it does, the original ruling is extended by analogy.

Examples frequently cited include the extension of the prohibition of wine to other intoxicants, on the grounds that they share the same intoxicating 'illat. Qiyas has also been used to address novel commercial, medical, or technological matters by applying rulings from established cases that involve similar underlying causes.

In Sunni Islam, all four traditional schools recognize qiyas to varying extents, with the Hanafi, Maliki, Shafi'i, and Hanbali schools developing differing rules on acceptable 'illat and on which matters may be analogized. In contrast, many Shi'i jurists reject qiyas as a general method, preferring Qur'an, Sunnah, and reason grounded in the explicit texts.

In modern jurisprudence, qiyas remains widely used where explicit texts are absent, though there is ongoing debate about its scope and the proper identification of 'illat. Contemporary discourse often incorporates maqasid al-sharia (goals of Islamic law) to guide or limit analogical reasoning.