The traditionist-jurisprudents (fuqahā' ashāb al-hadīth) of the earlier ninth century C.E. proposed that Islamic law be inferred from hadith, reports of what the Prophet, his leading Companions, and the Followers had said or done, without significant resort to reason. Contradictions among hadith reports they either resolved by means of isnād comparison or simply let stand, refusing to define the law by their own preferences. Their adversaries the rationalistic jurisprudents (ashāb al-ra'y) also used hadith, but far less extensively and without significant use of isnād comparison to sort out the sound from the unsound. In the later ninth century, rationalistic jurisprudents took up many of the forms formerly peculiar to the traditionist-jurisprudents, especially formal dependence on hadith and isnād comparison to sort the sound from the unsound. Traditionist-jurisprudents in turn accepted the need for separate expertise in legal reasoning besides hadith criticism. Although some developments took place independently of them, the history of Islamic law across the ninth century cannot be written without reference to the traditionist-jurisprudents and their strident advocacy of hadith.