«ولا دخل للعرض العام في التعريفات لأنه لا يفيد التميز»
A common accident has no place in these definitions because it does not distinguish the thing.
A common accident can be shared by different species. For example, being able to walk is not peculiar to humans; many other animals walk.
Calling a human simply “something that walks” therefore fails to pick out the human species. The required distinguishing function of definition is not achieved.