Description: Collection Principle. This remarkable theorem scheme is in effect a
very strong generalization of the Axiom of Replacement. The proof makes
use of Scott's trick scottex that collapses a proper class into a set
of minimum rank. The wff ph can be thought of as ph ( x , y ) .
Scheme "Collection Principle" of Jech p. 72. (Contributed by NM, 17-Oct-2003)