Computer Proofs in Gödel’s Class Theory with Equational Definitions for Composite and Cross

Some basic theorems about composition and other key constructs of set theory were proved using McCune’s computer program OTTER, building on Quaife’s modification of Gödel’s class theory. Our proofs use equational definitions in terms of Gödel’s flip and rotate functors. A new way to prove the composition of homomorphisms theorem is also presented.