This is the general idea behind category theory: it describes relations and not objects themselves.
That's quite a shift from set theory, where the core idea is that objects can be described with what's inside of them (and building the whole idea of relation as a set of tuples).
That's quite a shift from set theory, where the core idea is that objects can be described with what's inside of them (and building the whole idea of relation as a set of tuples).