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Description: If a formula holds for some value of a variable not occurring in it, then it holds for all values of that variable. (Contributed by BJ, 28-Dec-2020)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | ax5ea | ⊢ ( ∃ 𝑥 𝜑 → ∀ 𝑥 𝜑 ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | ax5e | ⊢ ( ∃ 𝑥 𝜑 → 𝜑 ) | |
| 2 | ax-5 | ⊢ ( 𝜑 → ∀ 𝑥 𝜑 ) | |
| 3 | 1 2 | syl | ⊢ ( ∃ 𝑥 𝜑 → ∀ 𝑥 𝜑 ) |