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Mirrors > Home > MPE Home > Th. List > con3 | Structured version Visualization version GIF version |
Description: Contraposition. Theorem *2.16 of [WhiteheadRussell] p. 103. This was the fourth axiom of Frege, specifically Proposition 28 of [Frege1879] p. 43. Its associated inference is con3i 154. (Contributed by NM, 29-Dec-1992.) (Proof shortened by Wolf Lammen, 13-Feb-2013.) |
Ref | Expression |
---|---|
con3 | ⊢ ((𝜑 → 𝜓) → (¬ 𝜓 → ¬ 𝜑)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | id 22 | . 2 ⊢ ((𝜑 → 𝜓) → (𝜑 → 𝜓)) | |
2 | 1 | con3d 152 | 1 ⊢ ((𝜑 → 𝜓) → (¬ 𝜓 → ¬ 𝜑)) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 → wi 4 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 |
This theorem is referenced by: pm2.65 192 con34b 316 nic-ax 1676 nic-axALT 1677 axc10 2385 camestres 2669 baroco 2672 rexim 3088 falseral0 4520 dfon2lem9 34763 hbntg 34777 naim1 35274 naim2 35275 lukshef-ax2 35300 bj-eximALT 35518 bj-axc10v 35671 ax12indn 37813 cvrexchlem 38290 cvratlem 38292 axfrege28 42580 vk15.4j 43289 tratrb 43297 hbntal 43314 tratrbVD 43622 con5VD 43661 vk15.4jVD 43675 nrhmzr 46647 |
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