Description: There does not exist exactly one set such that T. is true. (Contributed by Anthony Hart, 13-Sep-2011)
Ref | Expression | ||
---|---|---|---|
Assertion | neutru | ⊢ ¬ ∃! 𝑥 ⊤ |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | nexntru | ⊢ ¬ ∃ 𝑥 ¬ ⊤ | |
2 | eunex | ⊢ ( ∃! 𝑥 ⊤ → ∃ 𝑥 ¬ ⊤ ) | |
3 | 1 2 | mto | ⊢ ¬ ∃! 𝑥 ⊤ |