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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 157. (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 155 | 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: pm2.65 195 con34b 318 nic-ax 1670 nic-axALT 1671 axc10 2399 camestres 2756 baroco 2759 rexim 3241 falseral0 4459 dfon2lem9 33031 hbntg 33045 naim1 33732 naim2 33733 lukshef-ax2 33758 bj-eximALT 33969 bj-axc10v 34110 ax12indn 36073 cvrexchlem 36549 cvratlem 36551 axfrege28 40168 vk15.4j 40855 tratrb 40863 hbntal 40880 tratrbVD 41188 con5VD 41227 vk15.4jVD 41241 nrhmzr 44137 |
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