theorem ssabi {x: nat} (p q: wff x): $ p -> q $ > $ {x | p} C_ {x | q} $;
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ssab | A. x (p -> q) <-> {x | p} C_ {x | q} |
|
2 | hyp h | p -> q |
|
3 | 2 | ax_gen | A. x (p -> q) |
4 | 1, 3 | mpbi | {x | p} C_ {x | q} |