The patent system appears to make three ontological assumptions often associated with scientific realism: there is a natural world that is independent of human knowledge and technology; invented products can be unobservable things; and invented products have causal powers. Although a straightforward reading of patent laws implies these ontological commitments, it is not at all clear that what the patent system has to say about the world has any bearing on issues of scientific realism. While realists might embrace the patent (...) system’s apparent ontology as providing additional support for their view, anti-realists could propose an alternative interpretation of patent law that does not involve realist ontological commitments. Thus, questions about the patent system’s ontology depend on whether one takes patent laws at face value or defends an interpretation of patent law motivated by philosophical theory. Philosophers of science should pay attention to the practice of patenting, even if they ultimately reject the patent system’s apparent ontology and offer an alternative interpretation. (shrink)