(with Susan Rogerson) “Routes to Triviality,” Journal of Philosophical Logic, 33 (2004) 421–436.
It is well known that contraction-related principles trivialise naïve class theory. It is less well known that many other principles unrelated to contraction also render the theory trivial. This paper provides a characterisation of a large class of formulas which do the job. This class includes all properly implication formulas known in the literature, and adds countably many more.