Definition:Russell Class
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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
Source of Name
This entry was named for Bertrand Russell.
Sources
- 1971: Gaisi Takeuti and Wilson M. Zaring: Introduction to Axiomatic Set Theory: $\S 4.13$