section_path: Definition/Branches
section_name: Branches
paragraph_text: Branches
  
  The nature of metaphysics can also be characterized in relation to its main branches. An influential division from early modern philosophy distinguishes between general and special or specific metaphysics. General metaphysics, also called ontology, takes the widest perspective and studies the most fundamental aspects of being. It investigates the features that all entities have in common and how entities can be divided into different categories. Categories are the most general kinds, such as substance, property, relation, and fact. Ontologists research which categories there are, how they depend on one another, and how they form a system of categories that provides an encompassing classification of all entities.
  
  Special metaphysics considers being from more narrow perspectives and is divided into subdisciplines based on the perspective they take. Metaphysical cosmology examines changeable things and investigates how they are connected to form a world as a totality of entities extending through space and time. Rational psychology restricts itself to exploring metaphysical foundations and problems concerning the mind, such as its relation to matter and the freedom of the will. Natural theology studies the divine and its role as the first cause. The scope of special metaphysics overlaps with other philosophical disciplines and it is often not clear whether a topic belongs to it rather than to disciplines like philosophy of mind and theology.
  
  Applied metaphysics is a young subdiscipline. It belongs to applied philosophy and studies the applications of metaphysics, both within philosophy and other fields of inquiry. In ethics and philosophy of religion, it concerns topics like the ontological foundation of moral claims and religious doctrines. Applications outside philosophy include the use of ontologies in artificial intelligence, economics, and sociology to classify entities as well as questions in psychiatry and medicine about the metaphysical status of diseases.
  
  Meta-metaphysics is the metatheory of metaphysics and investigates the nature and methods of metaphysics. It also examines how metaphysics differs from other philosophical and scientific disciplines and how it is relevant to them. While the discussions of its topics have a long history in metaphysics, it has only recently developed into a systematic field of inquiry.