We made it up. Generative Realism does not embrace historical realism. Our multiple histories are the conceptual basis we use for our discourse. An important point of agreement between Generative Realism and the postmodernists is the rejection of scientific epistemological hegemony. Scientific methodology and its language are a socially constructed system of concepts, but not necessarily the only system.
Religion is another.
You could describe the whole world as God. Those theories are are not invalid just because they are not science. Art is another system of knowing reality. I recently saw the van Gogh collection in the Amsterdam museum and it is a particular view, or statement, of reality that is as valid as any other when held against the criterion of experience. In science, something is a true fact because its methodological observation says so.