There is a prevailing opinion that conjectural knowledge (zann) cannot be taken as a basis in determining the
fundamental theological principles among the theologians. However, from which sources and how to obtain certainty
(yaqīn) and which types of knowledge are definitive (qat‘ī) have been discussed extensively. Certain and conjectural
knowledge meet at a common point in terms of relying on evidence. Conjectural knowledge obtained via reasoning
and/or religious scripture that do not express certainty. While conjectural knowledge has been essentially related to the
concepts of estimation, doubt, belief and knowledge, by its in term of value, it is stands closer to the concepts of
knowledge and belief. Conjectural knowledge contains different degrees of certainty. When it is chosen to be more
certain, it is considered as a valid conjecture, when it is disregarded, it is considered as erroneous conjecture. If there is
no choice for its certainty, then it is called doubt (shakk). If the information/judgment obtained through reasoning
becomes fixed, unchangeable and in a coherence that does not allow it to be otherwise, then it is called definitive (qat‘ī)
knowledge. To achieve that, theologians generally used methods of argumentations like syllogism, induction, exhaustive
investigation and disjunction (al-sabr wa’l-taqsīm) to provide such knowledge about divinity and prophethood.
Theologians have used conjectural knowledge, which are based on endoxic (mashhūrāt), already granted (musallamāt)
and acceptance of authority (maqbūlāt), in their dialectics to persuade their discussants, rather than to justify the
fundamental theological issues of religion. While theologians mostly use rational proofs in theological issues, they also
gave significant place to the scriptural narrative that determines the creed. In this context, theologians accepted the
narrated evidence as binding and decisive, as long as it is certain in terms of both authenticity and implication.
Ultimately, the fundamental theological principles of religion are based on these narrative evidences. Although the
theologians do not accept single reports (khabar al-wahid) for their questionable authenticity, they also made inferences
regarding subjects of traditions (sam‘iyyāt). Acting from this perspective, theologians tried to justify with narrative
evidence rather than rational arguments on these issues such as torment in grave, intercession (shafā‘ah) and sirât,
which are mostly matters of eschatology and the unseen (ghayb). Finally, it has been concluded that the conjectural
knowledge is still valid in some secondary theological issues and the assumption that the conjectural knowledge has no
deduction value in theology is not absolute.