الإِنْشَاءُ إِمَّا طَلَبِيٌّ، أَوْ غَيْرُ طَلَبِيٍّ
Inshāʾ is either requestive (ṭalabī) or non-requestive.
فَالطَّلَبِيُّ: مَا يَسْتَدْعِي مَطْلُوبًا غَيْرَ حَاصِلٍ وَقْتَ الطَّلَبِ
Requestive inshāʾ calls for something not yet attained when the request is made.
“Not yet attained” refers to the requested realization, not to something eternally impossible. “اِكْتُبْ” asks the addressee to undertake writing. The request does not imply that writing can never take place.
Non-requestive inshāʾ does not directly call for such an action or attainment. Instances include praise and blame formulas, oaths, and certain contractual formulas.