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Mirrors > Home > ILE Home > Th. List > exmodc | GIF version |
Description: If existence is decidable, something exists or at most one exists. (Contributed by Jim Kingdon, 30-Jun-2018.) |
Ref | Expression |
---|---|
exmodc | ⊢ (DECID ∃𝑥𝜑 → (∃𝑥𝜑 ∨ ∃*𝑥𝜑)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-dc 830 | . 2 ⊢ (DECID ∃𝑥𝜑 ↔ (∃𝑥𝜑 ∨ ¬ ∃𝑥𝜑)) | |
2 | pm2.21 612 | . . . 4 ⊢ (¬ ∃𝑥𝜑 → (∃𝑥𝜑 → ∃!𝑥𝜑)) | |
3 | df-mo 2023 | . . . 4 ⊢ (∃*𝑥𝜑 ↔ (∃𝑥𝜑 → ∃!𝑥𝜑)) | |
4 | 2, 3 | sylibr 133 | . . 3 ⊢ (¬ ∃𝑥𝜑 → ∃*𝑥𝜑) |
5 | 4 | orim2i 756 | . 2 ⊢ ((∃𝑥𝜑 ∨ ¬ ∃𝑥𝜑) → (∃𝑥𝜑 ∨ ∃*𝑥𝜑)) |
6 | 1, 5 | sylbi 120 | 1 ⊢ (DECID ∃𝑥𝜑 → (∃𝑥𝜑 ∨ ∃*𝑥𝜑)) |
Colors of variables: wff set class |
Syntax hints: ¬ wn 3 → wi 4 ∨ wo 703 DECID wdc 829 ∃wex 1485 ∃!weu 2019 ∃*wmo 2020 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 ax-in2 610 ax-io 704 |
This theorem depends on definitions: df-bi 116 df-dc 830 df-mo 2023 |
This theorem is referenced by: (None) |
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