I am concerned, rather, that there should not be more things dreamt of in my philosophy than there actually are in heaven and earth.

Simons (1987) and Casati and Varzi (1999) show that the calculus of individuals can be grounded in either in a bit of set theory or in monadic predicates schematically employed. "The Calculus of Individuals and Its Uses" (with Henry S. OEG-0-9-310283-3721 (010) 1972.