which refers to a jurist's exertion in an attempt to arrive at a ruling on a particular question. The theory of Twelver Shia jurisprudence parallels that of Sunni schools with some differences, such as recognition of reason (ʿaql) as a source of law in place of qiyas and extension of the notion of sunnah to include traditions of the imams. Sources of Sharia Islamic scholar Sayyid Rashid Rida (1865 - 1935 C.E) lists the four basic sources of Islamic law, agreed upon by all Sunni Muslims:"the [well-known] sources of legislation in Islam are four: the Qur'an, the Sunnah, the consensus of the ummah and ijtihad undertaken by competent jurists" Quran: In Islam, the Quran is considered to be the most sacred source of law. Classical jurists held its textual integrity to be beyond doubt on account of it having been handed down by many people in each generation, which is known as "recurrence" or "concurrent transmission" (tawātur). Only several hundred verses of the Quran have direct legal relevance, and they are concentrated in a few specific areas such as inheritance, though other passages have been used as a source for general principles whose legal ramifications were elaborated by other means. Hadith: The body of hadith provides more detailed and practical legal guidance, but it was recognized early on that not all of them were authentic. Early Islamic scholars developed a methodology for evaluating their authenticity by assessing trustworthiness of the individuals listed in their transmission chains. These criteria narrowed down the vast corpus of prophetic traditions to several thousand "sound" hadiths, which were collected in several canonical compilations. The hadiths which enjoyed concurrent transmission were deemed unquestionably authentic; however, the vast majority of hadiths were handed down by only one or a few transmitters and were therefore seen to yield only probable knowledge. The uncertainty was further compounded by ambiguity of the language contained in some hadiths and Quranic passages. Disagreements on the relative merits and interpretation of the textual sources allowed legal scholars considerable leeway in formulating alternative rulings. Ijma: It is the consensus that could in principle elevate a ruling based on probable evidence to absolute certainty. This classical doctrine drew its authority from a series of hadiths stating that the Islamic community could never agree on an error. This form of consensus was technically defined as agreement of all competent jurists in any particular generation, acting as