Grounds for emergence of complicated hadith (al-ḥadīth al-mushkil)

The science of mushkil al-ḥadīth is one of the major sciences pertaining to hadith. Comprehension of difficult hadiths and attaining what the Infallibles have meant, require a logic and academic mechanism the first phase of which is awareness of the grounds of emergence of the problem and then following up the solution for difficulties of hadith.  Having deeply investigated the difficult traditions in the collection of Shi‘a and Sunni hadith sources, this writing has sought twelve grounds for emergence of mushkil al-ḥadīth under the following titles and has referred to the relevant fields: 1) involving damages; 2) oddity (gharāba) of the word; 3) polysemy; 4) existence of terms or expressions; 5) complexity of the structure; 6) metaphorical statement; 7) separation from indications; 8) the causes of issuance of hadith; 9) exaltedness of the content; 10) the tradition being specialized; 11) intrinsic difference and discord; 12) extrinsic contradiction and discord.