Definition:Russell Class

Definition

The Russell class, denoted $\operatorname{Ru}$, equals the class of all sets $x$ that are not elements of themselves:

$\operatorname{Ru} = \set {x: x \notin x}$

Also see

• Russell's Paradox

Source of Name

This entry was named for Bertrand Russell.

Sources

• 1971: Gaisi Takeuti and Wilson M. Zaring: Introduction to Axiomatic Set Theory: $\S 4.13$