Necessary knowledge can be contrasted with inferential knowledge, meaning knowledge obtained without a deliberate proof versus knowledge reached by reasoning through premises.
But classical authors also contrast “necessary” with acquired (iktisābī) knowledge, shifting attention from the presence of an argument to the role of a person's choice and effort in obtaining it.
These classifications need not coincide. Before discussing a disputed example, identify whether “necessary” means “without inference” or “not produced through chosen acquisition.”