In his tenure as judge and jurist, Averroes for the most part ruled and gave fatwas according to the Maliki school of Islamic law which was dominant in Al-Andalus and the western Islamic world during his time. However, he frequently acted as "his own man", including sometimes rejecting the "consensus of the people of Medina " argument that is one of the traditional Maliki position. In Bidāyat al-Mujtahid, one of his major contributions to the field of Islamic law, he not only describes the differences between various school of Islamic laws but also tries to theoretically explain the reasons for the difference and why they are inevitable. Even though all the schools of Islamic law are ultimately rooted in the Quran and hadith, there are "causes that necessitate differences" (al-asbab al-lati awjabat al-ikhtilaf). They include differences in interpreting scripture in a general or specific sense, in interpreting scriptural commands as obligatory or merely recommended, or prohibitions as discouragement or total prohibition, as well as ambiguities in the meaning of words or expressions. Averroes also writes that the application of qiyas (reasoning by analogy) could give rise to different legal opinion because jurists might disagree on the applicability of certain analogies and different analogies might contradict each other.