Letters to the FOM list

Here are some letters of mine to the FOM (Foundations of Mathematics) list maintained by Steve Simpson:

intuitive vs. mathematical "sets"
CH not a problem for realism
intuitive motivation for NFU (1)
more NF stuff
intuitive motivation for NFU (2)
reference of mathematical propositions
discussion of my book
second order logic not a myth
formal and informal mathematics
sterility of 2nd order logic?
identity conditions of predicates
not denouncing formalized mathematics
second-order logic lives!
arbitrary properties not a problem
2nd order logic and reference, definitions
foundations in NFU
category of sets not cartesian closed in NFU