Di antara para Imam ada yang mengembangkan sejumlah kaidah yang diperselisihkan, yang mereka jadikan dasar bagi sebagian hukum mereka. Akibatnya, baik hukum-hukumnya maupun kaidah-kaidahnya menjadi sumber perbedaan di kalangan ahli fikih. Misalnya, mayoritas ahli fikih mengakui keabsahan Ijma' di kalangan generasi setelah para Sahabat, tetapi Imam asy-Syafi'i mempertanyakan terjadinya Ijma' tersebut, sementara Imam Ahmad menolaknya secara mutlak. Demikian pula, mayoritas ahli fikih menolak sandaran Imam Malik pada adat kebiasaan penduduk Madinah sebagai sumber penetapan hukum. Dan kaidah Istihsan dari Imam Abu Hanifah serta Istislah dari Malik, keduanya dilarang oleh Imam asy-Syafi'i karena dianggap terlalu bebas dari Al-Qur'an, Sunnah, dan Ijma'. Dengan kata lain, menurut pendapatnya, mereka terlalu banyak bersandar pada penalaran manusia.

There were among the Imaams some who developed a number of controversial principles on which they based some of their rulings. As a result, both the rulings and the principles became source of differences among jurists. For example, the majority of jurists recognized the validity of Ijmaa’ among the generations after the Sahaabah, but Imaam ash-Shaafi’ee questioned its occurrence while Imaam Ahmad rejected it outright. Similarly the majority of jurists rejected Imaam Maalikreliance on the customs of the Madeenites as a source of legislation. And Imaam Abu Haneefah’s principle of Istihsaan and Maalik’s Istislaah were both disallowed by Imaam ash-Shaafi’ee as being too independent of the Qur’aan, the Sunnah, and Ijmaa’. That is to say, they relied too much, in his opinion, on human reasoning.

Di sisi lain, Imam asy-Syafi'i berpendapat bahwa pendapat para Sahabat wajib diterima dalam masalah hukum, sedangkan yang lain berpendapat bahwa itu hanyalah ijtihad mereka yang tidak mengikat generasi-generasi setelahnya.181

On the other hand, Imaam ash-Shaafi’ee felt that the opinion of the Sahaabah had to be accepted on legal matters, while others felt that it was only reasoning on their part which was not binding later generations.181