Self-reference paradox
A critique of set theory's flaws. It arose from the axiom that a set can contain everything. It was resolved by the axiom that a set of sets is no longer considered a set.
Some things are too large to be sets. In other words, some concepts are too large to be elements of a set. Therefore, Russell's paradox is treated as a forbidden definition accordingly. Thus, sets cannot be defined arbitrarily but must be well-defined. This simultaneously means that non-symbolized language cannot be the basis for mathematical definitions.

Seonglae Cho
