Recall that conceptual knowledge is knowledge of a single meaning. Necessarily then, each concept is distinct from all others. For if concepts could not be distinguished from one another, then they wouldn’t have been knowable.
For example: if you could not distinguish between the meanings of “pen”, “paper”, and “eraser”, then you would not know what those terms mean.
The fact that a defining distinction is established for all concepts, is the basis for the law of identity (Qanun Al-Huwiya).
The Law of Identity
The law of identity dictates that a thing is itself, and is therefore distinct from what is other than itself. That which makes a thing itself, is called the thing’s essence (Mahia).
For example: the essence of an even number, is that it is an integer that is divisible by two. If a thing is not an integer that is divisible by two, then it is not an even number.