Modal structuralism offers a program of interpretation of mathematics which incorporates two features: (a) an emphasis on structures as the main subject-matter of mathematics, and (b) a complete elimination of reference to mathematical objects by interpreting mathematics in terms of modal logic (as first suggested by Putnam (1967), and developed in Hellman (1989, 1996)). Given these features, the resulting approach is called a modal-structural interpretation (Hellman 1989, pp. vii–viii and 6–9).