Metaphysics is the study of reality. Reality is that which exists. As well as asking, "What exists?," metaphysics raises questions about the nature of what exists, i.e. what kinds of entities populate the universe as well as the nature of the relationships between them. An entity can be an object, but it could also be a property, event, force, etc.
More generally, metaphysics concerns questions about reality beyond what science can discover, e.g. whether electrons exist is a question for physics, but, whether objects exist is a question for metaphysics. There are several branches, some of which are:
- Ontology, which tries to sort 'real' entities from appearances and differentiates entities into logical categories, e.g. ‘properties’, ‘physical objects’, ‘numbers’, etc.
- Semantics, which is the study of the relationship between entities and thoughts about them, as well as the language used to express those thoughts. Issues about truth emerge from semantic inquiry. If a sentence successfully corresponds to reality, then the metaphysical claim is said to be true (according to one of the many theories of truth), e.g. 'Snow is white.' is a true sentence if and only if snow, in fact, is white and false if snow, in fact, is not white. Issues of reference are also semantic concerns. If a term successfully corresponds to reality, then it is said to refer. However, terms referring to unicorns or the Easter Bunny are vacuous since these entities do not really exist. What a term means goes beyond what the term refers to, rather, it is the sense (or senses) in which it is understood. Historically it has been thought that one would not know what a term meant without also knowing what to expect if it were true.
- Mereology, which is the study of parts and wholes, and the manner in which they are related. Is a whole identical with the sum of its parts? If it was, then that would entail that both the parts and the whole have the same properties, but, this doesn't seem to be the case, e.g. water is wet but each water molecule that comprises it is not wet.
- Teleology, which assumes a purposiveness in nature, is the study of what the universe and its constituents are for. For example, Aristotle asserted that the goal of all human beings is to be happy, so, all our actions are directed toward the ultimate goal of being happy. This is what our actions are for.
