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Mirrors > Home > ILE Home > Th. List > dfnot | GIF version |
Description: Given falsum, we can define the negation of a wff 𝜑 as the statement that a contradiction follows from assuming 𝜑. (Contributed by Mario Carneiro, 9-Feb-2017.) (Proof shortened by Wolf Lammen, 21-Jul-2019.) |
Ref | Expression |
---|---|
dfnot | ⊢ (¬ 𝜑 ↔ (𝜑 → ⊥)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | fal 1291 | . 2 ⊢ ¬ ⊥ | |
2 | mtt 642 | . 2 ⊢ (¬ ⊥ → (¬ 𝜑 ↔ (𝜑 → ⊥))) | |
3 | 1, 2 | ax-mp 7 | 1 ⊢ (¬ 𝜑 ↔ (𝜑 → ⊥)) |
Colors of variables: wff set class |
Syntax hints: ¬ wn 3 → wi 4 ↔ wb 103 ⊥wfal 1289 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 104 ax-ia2 105 ax-ia3 106 ax-in1 576 ax-in2 577 |
This theorem depends on definitions: df-bi 115 df-tru 1287 df-fal 1290 |
This theorem is referenced by: inegd 1303 pclem6 1305 alnex 1428 alexim 1576 difin 3201 indifdir 3220 recvguniq 9881 bj-axempty2 10685 |
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