A call to cj i th, where th has the form
|- !x1 .. xn. p1 /\ .. /\ pm ==> !y... q1 /\ .. ==> ... ==>
c1 /\ c2 /\ ... ck
returns the theorem
|- !x1 .. xn. p1 /\ .. /\ pm ==> !y... q1 /\ .. ==> ... ==> ci
Note that the indexing starts at 1. The conjuncts are stripped apart
without regard to the way in which they are associated, as per the
behaviour of CONJUNCTS.