If you’ve ever had a traditional logic course, you’ll have run into “The Law of Identity” as the founding principle of all Western thought. It says that:
“To be is to be something in particular; to be nothing in particular or anything in general, is to be nothing at all.”
This usually gets expressed as “A = A” thanks to Ayn Rand’s Objectivism and credited to Aristotle. You want to dig a little deeper, however, it actually predates Aristotle’s laws of logic.
More to the point, this is why we have keys in the relational data model and why those