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Mirrors > Home > ILE Home > Th. List > nfv | GIF version |
Description: If x is not present in φ, then x is not free in φ. (Contributed by Mario Carneiro, 11-Aug-2016.) |
Ref | Expression |
---|---|
nfv | ⊢ Ⅎxφ |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ax-17 1416 | . 2 ⊢ (φ → ∀xφ) | |
2 | 1 | nfi 1348 | 1 ⊢ Ⅎxφ |
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