Because Muslim scholars differed on, some of the secondary sources of the law and the principles for interpreting those sources, different schools of law arose in Islam. At first fairly numerous, these schools began to arise before 700 under the Umayyads and continued to proliferate until about 950. After that time some schools began to die out. There are now four Sunni schools: Hahafi, Maliki, Shafi'i, and Hanbali; three Shi'i schools: Ja'fari or Imami, Zaydi, and Isma'ili (the last of which is considered heterodox by most other, Muslims); and one Kharijite school (Ibadi). Over the centuries there have been sporadic efforts to re-establish a fifth Sunni school, the literalist Zahiri school.

Historically, the various schools differ according to their principles for the use and interpretation of the- four sources of law (the Qur'an, the Sunnah (traditions), consensus, and analogy). Some schools...