Structuralism in the philosophy of science comes in many varieties. It ranges from a methodological thesis (concerning the nature of scientific theories and claiming that they are best understood as families of models) to an ontic position (concerning what there is and claiming that structure is all there is). In between, there is an epistemic view: there is more to the world than structure, but of this more nothing but its structure can be known. In this chapter, I shall discuss the radical ontic position. As noted already towards the end of the last chapter, ontic structuralism (henceforth OS) is still quite an amorphous, though suggestive, position. The slogan is: "all that there is, is structure" (da Costa and French 2003, 189). But then there are different claims of varying strengths. Here are some of them.