ومنها أخذ ما بالعرض مكان ما بالذات
Another error is substituting what holds accidentally for what holds essentially.
Bi-l-dhāt concerns a predicate considered as belonging to a thing in its own relevant respect. Bi-l-ʿaraḍ concerns something attributed to it through a secondary relation or circumstance.
If a term is used in an essential sense in one premise and through an accidental relation in another, it no longer functions as a uniform middle term. The respective modes of predication cannot simply be merged.