proper axiomatization of "mem" -- do not leave it formally unspecified;
proper axiomatization of "mem" -- do not leave it formally unspecified;

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle