Class

Proper class

A proper class is a Class which is not the element of any other class, and therefore not a set. If elementhood is defined by

𝔈⁡(𝑥)def⟺(∃ℭ𝔩𝔰⁡𝑦)[𝑥∈𝑦]

then a proper class 𝐴 satisfies ¬𝔈⁡(𝐴).

#state/tidy | #lang/en | #SemBr