In Parts of Classes, David Lewis outlined a reduction of ZFC to a second order mereology. His conclusion takes on the following form in this reconstruction: ZFC is susceptible to parameterized interpretation in M (classical second order mereology) plus, there is a strongly inaccessible partition. The proof makes use of the fact that ordered pairs in M plus an infinite partition are susceptible to parameterized interpretation.

Philipp Werner, München, Deutschland.