Al-Shafii's rejection of istihsan did more than settle one technical dispute inside early Islamic jurisprudence, since An Introduction to Islamic Law credits the argument, and the wider methodological project surrounding it, with effectively founding usul al-fiqh, Islamic legal theory, as a discipline in its own right rather than leaving legal reasoning as an unexamined craft passed down by example. The Formation of the Sunni Schools of Law traces how the dispute between al-Shafii and the Iraqi jurists over istihsan became a reference point for later generations of scholars across every Sunni school, including the Hanafis whose early use of the concept had prompted the critique, since even jurists who continued to employ a version of istihsan afterward did so under pressure to defend it against exactly the charge al-Shafii had raised. The Canonization of Islamic Law: A Social and Intellectual History notes that the debate helped fix a lasting expectation across Sunni legal culture that a ruling must be traceable to a stated source and method, an expectation that outlived the specific historical argument between al-Shafii and the school he was arguing against and became part of how Islamic jurisprudence as a whole came to judge the legitimacy of a legal conclusion.