What are the rulings for that which is probabilistic in authenticity and probabilistic in indication, and for that which is definitive in authenticity and definitive in indication, and by what names are these rulings known?

Scholars of Usul (Islamic legal theory) discuss the ranks of legal proofs. Some are definitive in authenticity (qat'i al-thubut), such as the Qur'an and mutawatir Sunnah (narrations transmitted by so many people that they are beyond doubt). Others are presumptive in authenticity (zanni al-thubut), such as Ahadith al-Ahad (single-chain narrations). As for definitive in meaning (qat'i al-dalalah), it refers to a text that has only one possible meaning. Presumptive in meaning (zanni al-dalalah) refers to a text that admits more than one interpretation.

The highest rank of texts is that which is definitive in both authenticity and meaning. The rank decreases when either one or both become presumptive. Thus, there are four types of proofs: - Definitive in authenticity and meaning: such as mutawatir texts. - Definitive in authenticity, presumptive in meaning: such as verses that require interpretation. - Presumptive in authenticity, definitive in meaning: such as Ahad (single-chain) narrations with a definitive understanding. - Presumptive in authenticity and meaning: such as Ahad (single-chain) narrations with a presumptive understanding.

The entire Qur'an is definitive in authenticity. Some parts of it are definitive in meaning, and some are presumptive. As for the Sunnah, some parts are definitive in authenticity, and some are presumptive. Both types may be definitive in meaning or presumptive. What is definitive in both authenticity and meaning leaves no room for ijtihad (independent reasoning). However, what is presumptive in either one or both is a field for scholarly ijtihad.