 Philosophy is a science of possible and actual reality. According to Wolff’s own taxonomy, theoretical philosophy is divided into three separate branches: ontology (or metaphysics proper), special metaphysics, and physics. Cosmology, as a branch of metaphysics, is a special or restricted science insofar as its subject matter deals with the “world-whole” rather than “being in general” (the subject matter of ontology). Although there is an important sense for Wolff in which ontology is relevant for, and even necessarily grounds cosmology and the other special sciences, cosmology (itself) stands in a grounding relationship to physics that is, yet again, a more narrow and specialized discipline (Cosm. §121). Just as there are certain principles and certain truths established in ontology that are relevant for cosmology, there are certain principles and certain truths established in cosmology that are relevant for the more specialized science of physics. In fact, within Wolff’s system there is complete uniformity from the top-down (so to speak), so that even principles of ontology are relevant for the discipline of physics.