 This puts us in a position to return to Hellman’s 2003 challenge. The question of whether category theory can be used to formulate a version of philosophical structuralism is, in his view, directly related to the presumed autonomy of these new approaches from traditional set theory. Building on Feferman (1977), he formulates two general objections. Following Linnebo &amp; Pettigrew (2011), we can call the first the “logical dependence” objection. Its core is the argument that category theory, general topos theory, etc. are not autonomous of set theory in the end. The reason is that the axiomatic specification of categories and topoi presupposes the primitive concepts of operation, collection, and function, and the latter need to be defined in a set theory such as ZFC. Categorical foundations are therefore dependent on non-structural set theory.