working procedures for distinguishing commonalities and unity of differences

identifying the chain of transmitters mentioned in the sanads for the verification of the sanad is necessary for employment of ḥadīth. one of the problems observed in the chains of transmission is the repetition of the names applicable to two or more transmitters. on the other hands, some transmitters have been referred to by various names and titles in chains of transmission; various titles that are all denoting one single person. the discourse of distinguishing the commonalities and unity of differences and the equalization of various transmitters in identification of the transmitter and analyzing and evaluating the chain of transmission by the scholars is done in special procedures. rijāl experts have dedicated part of their attempts to this issue and have considered some procedures as among the procedures for distinction of commonalities and unity of differences, including paying attention to the transmitter’s class; the existence of titles independently in rijālī books, especially in najāshī rijāl; difference in ṭarīq (chain of transmission) and being the transmitter of the book; existence of difference in the transmitter and the one from whom the ḥadīth is transmitted; knowledge of the nicknames, entitlements, and the geographical situation of cities; attention to the probable misrepresentations (taṣḥīfs) etc.