Metaphysics is the branch of philosophy that studies the fundamental nature of reality. This includes studies of the first principles of: being or existence, identity, change, consciousness, space and time, necessity, actuality, and possibility. It can also include questions about the existence of God, as well as relationships between foundational philosophical ideas such as between mind and matter, cause and effect, substance and attribute, or potentiality and actuality.
In metaphysics, ontology is the philosophical study of being. It investigates what types of entities exist, how they are grouped into categories, and how they are related to one another on the most fundamental level. Ontologists often try to determine what the categories or highest kinds are and how they form a system of categories that encompasses the classification of all entities. Commonly proposed categories include substances, properties, relations, states of affairs, and events. These categories are characterized by fundamental ontological concepts, including particularity and universality, abstractness and concreteness, or possibility and necessity. Of special interest is the concept of ontological dependence, which determines whether the entities of a category exist on the most fundamental level. Disagreements within ontology are often about whether entities belonging to a certain category exist and, if so, how they are related to other entities.
In logic, philosophy and related fields, mereology is the study of parts and the wholes they form. Whereas set theory is founded on the membership relation between a set and its elements, mereology emphasizes the meronomic relation between entities, which—from a set-theoretic perspective—is closer to the concept of inclusion between sets.
Roderick Milton Chisholm was an American philosopher known for his work on epistemology, metaphysics, free will, value theory, and the philosophy of perception.
In logic and philosophy, a property is a characteristic of an object; a red object is said to have the property of redness. The property may be considered a form of object in its own right, able to possess other properties. A property, however, differs from individual objects in that it may be instantiated, and often in more than one object. It differs from the logical/mathematical concept of class by not having any concept of extensionality, and from the philosophical concept of class in that a property is considered to be distinct from the objects which possess it. Understanding how different individual entities can in some sense have some of the same properties is the basis of the problem of universals.
In formal ontology, a branch of metaphysics, and in ontological computer science, mereotopology is a first-order theory, embodying mereological and topological concepts, of the relations among wholes, parts, parts of parts, and the boundaries between parts.
Peter van Inwagen is an American analytic philosopher and the John Cardinal O'Hara Professor of Philosophy at the University of Notre Dame. He is also a research professor of philosophy at Duke University each spring. He previously taught at Syracuse University, earning his PhD from the University of Rochester in 1969 under the direction of Richard Taylor. Van Inwagen is one of the leading figures in contemporary metaphysics, philosophy of religion, and philosophy of action. He was the president of the Society of Christian Philosophers from 2010 to 2013.
In computer science, object composition and object aggregation are closely related ways to combine objects or data types into more complex ones. In conversation the distinction between composition and aggregation is often ignored. Common kinds of compositions are objects used in object-oriented programming, tagged unions, sets, sequences, and various graph structures. Object compositions relate to, but are not the same as, data structures.
Perdurantism or perdurance theory is a philosophical theory of persistence and identity. The debate over persistence currently involves three competing theories—one three-dimensionalist theory called "endurantism" and two four-dimensionalist theories called "perdurantism" and "exdurantism". For a perdurantist, all objects are considered to be four-dimensional worms and they make up the different regions of spacetime. It is a fusion of all the perdurant's instantaneous time slices compiled and blended into a complete mereological whole. Perdurantism posits that temporal parts alone are what ultimately change. Katherine Hawley in How Things Persist states that change is "the possession of different properties by different temporal parts of an object".
In philosophy, mereological nihilism is the metaphysical thesis that there are no objects with proper parts. Equivalently, mereological nihilism says that mereological simples, or objects without any proper parts, are the only material objects that exist. Mereological nihilism is distinct from ordinary nihilism insofar as ordinary nihilism typically focuses on the nonexistence of common metaphysical assumptions such as ethical truths and objective meaning, rather than the nonexistence of composite objects.
Metaphysical nihilism is the philosophical theory that there might have been no objects at all—that is, that there is a possible world in which there are no objects at all; or at least that there might have been no concrete objects at all, so that even if every possible world contains some objects, there is at least one that contains only abstract objects.
In philosophy, the term formal ontology is used to refer to an ontology defined by axioms in a formal language with the goal to provide an unbiased view on reality, which can help the modeler of domain- or application-specific ontologies to avoid possibly erroneous ontological assumptions encountered in modeling large-scale ontologies.
In contemporary mereology, a simple is any thing that has no proper parts. Sometimes the term "atom" is used, although in recent years the term "simple" has become the standard.
In contemporary metaphysics, temporal parts are the parts of an object that exist in time. A temporal part would be something like "the first year of a person's life", or "all of a table from between 10:00 a.m. on June 21, 1994 to 11:00 p.m. on July 23, 1996". The term is used in the debate over the persistence of material objects. Objects typically have parts that exist in space—a human body, for example, has spatial parts like hands, feet, and legs. Some metaphysicists believe objects have temporal parts as well.
In philosophy, mereological essentialism is a mereological thesis about the relationship between wholes, their parts, and the conditions of their persistence. According to mereological essentialism, objects have their parts necessarily. If an object were to lose or gain a part, it would cease to exist; it would no longer be the original object but a new and different one.
Metaontology or meta-ontology is the study of the field of inquiry known as ontology. The goal of meta-ontology is to clarify what ontology is about and how to interpret the meaning of ontological claims. Different meta-ontological theories disagree on what the goal of ontology is and whether a given issue or theory lies within the scope of ontology. There is no universal agreement whether meta-ontology is a separate field of inquiry besides ontology or whether it is just one branch of ontology.
Jonathan Schaffer is an American philosopher specializing in metaphysics and also working in epistemology, mind, and language. He is best known for his work on grounding and his development of monism, and is also a notable proponent of contrastivism.
In philosophy, specifically in the area of metaphysics, counterpart theory is an alternative to standard (Kripkean) possible-worlds semantics for interpreting quantified modal logic. Counterpart theory still presupposes possible worlds, but differs in certain important respects from the Kripkean view. The form of the theory most commonly cited was developed by David Lewis, first in a paper and later in his book On the Plurality of Worlds.
The following outline is provided as an overview of and topical guide to metaphysics:
In mereology, an area of philosophical logic, the term gunk applies to any whole whose parts all have further proper parts. That is, a gunky object is not made of indivisible atoms or simples. Because parthood is transitive, any part of gunk is itself gunk.
Van Cleve, J. (2008). The moon and sixpence: a defense of mereological universalism. Varzi, Achille, "Mereology", The Stanford Encyclopedia of Philosophy (Winter 2016 Edition), Edward N. Zalta (ed.), forthcoming URL = <https://plato.stanford.edu/archives/win2016/entries/mereology/>.
