Abstract
In this article, istiḥsān, which is an evidence of nahiv method, is examined and its definition, types and source value are mentioned. Istiḥsān is to make an exceptional judgment in the judgment of a minor issue based on specific evidence. Istiḥsān is to oppose an open syllogism. This definition is taken from the fiqh method. In this context, istiḥsān includes making an exceptional judgment on language issues, unlike its counterparts. Istiḥsān is accepted as a mental evidence and there are many examples in nahiv sources. In the nahiv method, the evidence of istiḥsān is used when a linguistic use other than the syllogism or the original rule requires it. Linguists have explained the origins of istiḥsān with reasons such as allocating a malady, preferring the heavy one instead of the light one, pointing out the main word of the word, abandoning the main analogy due to an evidence, leaving the sema evidence and accepting the exceptional provision. This evidence was seen as weak by linguists as it is not regular and generalizable; but it is considered as an acceptable evidence even if it is of secondary nature. It is thought that Ibn Jinnī (d. 392/1002) was the first to emphasize this evidence under a separate title. According to her, although this evidence is weak, it adds a breadth to the speech and offers an explanatory model in linguistic reasoning.