| 1:: | |- (. ( ( ph /\ ps ) -> ( ch <-> th ) )
     ->. ( ( ph /\ ps ) -> ( ch <-> th ) ) ). | 
 | 2:: | |- (. ( ( ph /\ ps ) -> ( ch <-> th ) ) ,.
     ( ph /\ ps ) ->. ( ph /\ ps ) ). | 
 | 3:: | |- (. ( ( ph /\ ps ) -> ( ch <-> th ) ) ,.
     ( ph /\ ps ) , th ->. th ). | 
 | 5:1,2,?: e12 | |- (. ( ( ph /\ ps ) -> ( ch
     <-> th ) ) , ( ph /\ ps )  ->. ( ch <-> th ) ). | 
 | 6:3,5,?: e32 | |- (. ( ( ph /\ ps ) -> ( ch
     <-> th ) ) , ( ph /\ ps ) , th ->. ch ). | 
 | 7:6: | |- (. ( ( ph /\ ps ) -> ( ch
     <-> th ) ) , ( ph /\ ps ) ->. ( th -> ch ) ). | 
 | 8:7: | |- (. ( ( ph /\ ps ) -> ( ch <-> th ) )
     ->. ( ( ph /\ ps ) -> ( th -> ch ) ) ). | 
 | 9:8,?: e1a | |- (. ( ( ph /\ ps ) -> ( ch
     <-> th ) ) ->. ( ph -> ( ps -> ( th -> ch ) ) ) ). | 
 | qed:9: | |- ( ( ( ph /\ ps ) -> ( ch <-> th ) )
     -> ( ph -> ( ps -> ( th -> ch ) ) ) ) |