Complement of Universe is Empty Set

Theorem

The complement of the universe is the empty set:

$\complement \paren {\mathbb U} = \O$

Proof

Substitute $\mathbb U$ for $S$ in $\complement_S \paren S = \O$ from Relative Complement with Self is Empty Set.

$\blacksquare$

Also see

• Complement of Empty Set is Universe

Sources

• 1967: George McCarty: Topology: An Introduction with Application to Topological Groups ... (previous) ... (next): $\text{I}$: Exercise $\text{B i}$
• 1977: Gary Chartrand: Introductory Graph Theory ... (previous) ... (next): Appendix $\text{A}.1$: Sets and Subsets
• 1978: Thomas A. Whitelaw: An Introduction to Abstract Algebra ... (previous) ... (next): $\S 6.6$: Subsets
• 2008: Paul Halmos and Steven Givant: Introduction to Boolean Algebras ... (previous) ... (next): $\S 2$