  The considerations from physics do not logically compel us to abandon the idea of a world of distinct ontologically subsistent individuals with intrinsic properties. The identity and individuality of quantum particles could be grounded in each having a primitive thisness, and the same could be true of spacetime points. Physics does seem to tell us that certain aspects of such a world would be unknowable. The epistemic structural realist thinks that all we can know is structure, but it is the structure of an unknowable realm of individuals. An epistemic structural realist may insist in a Kantian spirit that there being such objects is a necessary condition for our empirical knowledge of the world. It may be argued that it is impossible to conceive of relational structures without making models of them in terms of domains of individuals. Certainly, the structuralist faces a challenge in articulating her views to contemporary philosophers schooled in modern logic and set theory, which retains the classical framework of individual objects, and where a structure is just a particular set, namely a set of objects, and a set of relations, where the latter are thought of extensionally as just sets of ordered pairs (or more generally n-tuples in the case of n-place relations).