The four source hierarchy al-Shafii argued for in the Risala did not remain confined to the Shafii school he founded, and An Introduction to Islamic Law records that some version of the same ordering, Quran, Sunna, consensus and analogy, came to structure legal theory across the Sunni schools broadly, even where a given school continued to recognise additional secondary instruments, such as the Hanafi use of istihsan, alongside the core four. The Formation of the Sunni Schools of Law situates this spread as evidence of how thoroughly al-Shafii's methodological argument reshaped the terms on which Islamic legal reasoning was conducted, so that later jurists in every school felt obliged to state where a ruling stood within, or in relation to, a four source framework whether or not they accepted every element of al-Shafii's own position on it. The Canonization of Islamic Law: A Social and Intellectual History notes that this is why al-Shafii is remembered less as the founder of one school among several equally weighted alternatives than as the jurist who gave Islamic legal theory its basic vocabulary, a framework other schools have argued within and against for over a thousand years rather than one they simply ignored.