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Mirrors > Home > MPE Home > Th. List > Mathboxes > frege42 | Structured version Visualization version GIF version |
Description: Not not id 22. Proposition 42 of [Frege1879] p. 47. (Contributed by RP, 24-Dec-2019.) (Proof modification is discouraged.) |
Ref | Expression |
---|---|
frege42 | ⊢ ¬ ¬ (𝜑 → 𝜑) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | frege27 41143 | . 2 ⊢ (𝜑 → 𝜑) | |
2 | ax-frege41 41177 | . 2 ⊢ ((𝜑 → 𝜑) → ¬ ¬ (𝜑 → 𝜑)) | |
3 | 1, 2 | ax-mp 5 | 1 ⊢ ¬ ¬ (𝜑 → 𝜑) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 → wi 4 |
This theorem was proved from axioms: ax-mp 5 ax-frege1 41122 ax-frege8 41141 ax-frege41 41177 |
This theorem is referenced by: frege43 41179 |
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