Description: Syllogism between pm2.18 and pm2.24 . Proposition 39 of Frege1879 p. 46. (Contributed by RP, 24-Dec-2019) (Proof modification is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | frege39 | |- ( ( -. ph -> ph ) -> ( -. ph -> ps ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | frege38 | |- ( -. ph -> ( ph -> ps ) ) |
|
| 2 | ax-frege2 | |- ( ( -. ph -> ( ph -> ps ) ) -> ( ( -. ph -> ph ) -> ( -. ph -> ps ) ) ) |
|
| 3 | 1 2 | ax-mp | |- ( ( -. ph -> ph ) -> ( -. ph -> ps ) ) |