SELECT_RULE : thm -> thm
A |- ?x. P ------------------ SELECT_RULE A |- P[(@x.P)/x]
|- ?f. ONE_ONE f /\ ~ONTO fApplying SELECT_RULE to this theorem returns the following.
#SELECT_RULE INFINITY_AX; |- ONE_ONE(@f. ONE_ONE f /\ ~ONTO f) /\ ~ONTO(@f. ONE_ONE f /\ ~ONTO f)