Editing Metaphysics (section)

== Topics ==
=== Existence and categories of being ===
{{main|Existence|Theory of categories}}

Metaphysicians often regard existence or being as one of the most basic and general concepts.<ref>{{multiref | {{harvnb|Lowe|2005b|p=277}} | {{harvnb|White|2019|pp=135, 200}} | {{harvnb|Jubien|2004|pp=[https://books.google.com/books?id=uoCh8mpbZO4C&pg=PA47 47–48]}} }}</ref> To exist means to be part of [[reality]], distinguishing real entities from imaginary ones.<ref>{{multiref | {{harvnb|Lowe|2005b|p=277}} | {{harvnb|AHD staff|2022}} }}</ref> According to a traditionally influential view, existence is a property of properties: if an entity exists then its properties are instantiated.<ref>{{multiref |1={{harvnb|Casati|Fujikawa|loc=Lead Section, §1. Existence as a Second-Order Property and Its Relation to Quantification}} |2={{harvnb|Blackburn|2008|loc=[https://www.oxfordreference.com/display/10.1093/oi/authority.20110803095804522;jsessionid=AEB41DBFF0B3EBCDCCB8A1E0DAFD4EB0 existence]}} }}</ref> A different position states that existence is a property of individuals, meaning that it is similar to other properties, such as shape or size.<ref>{{multiref |1={{harvnb|Casati|Fujikawa|loc=Lead Section, §2. Existence as a First-Order Property and Its Relation to Quantification}} |2={{harvnb|Blackburn|2008|loc=[https://www.oxfordreference.com/display/10.1093/oi/authority.20110803095804522;jsessionid=AEB41DBFF0B3EBCDCCB8A1E0DAFD4EB0 existence]}} }}</ref> It is controversial whether all entities have this property. According to philosopher [[Alexius Meinong]], there are [[nonexistent objects]], including merely possible objects like [[Santa Claus]] and [[Pegasus]].<ref name="auto">{{multiref |1={{harvnb|Van Inwagen|2023}} |2={{harvnb|Nelson|2022|loc=Lead Section, §2. Meinongianism}} |3={{harvnb|Jubien|2004|p=[https://books.google.com/books?id=uoCh8mpbZO4C&pg=PA49 49]}} }}</ref>{{efn|According to Meinong, existence is not a synonym of being: all entities have being but not all entities have existence.<ref name="auto"/>}} A related question is whether existence is the same for all entities or whether there are different modes or degrees of existence.<ref>{{multiref |1={{harvnb|Casati|Fujikawa|loc=Lead Section, §3. How Many Ways of Being Existent?}} |2={{harvnb|McDaniel|2017|p=[https://books.google.com/books?id=8F0vDwAAQBAJ&pg=PT89 77]}} }}</ref> For instance, Plato held that [[Platonic forms]], which are perfect and immutable ideas, have a higher degree of existence than matter, which can only imperfectly reflect Platonic forms.<ref>{{multiref |1={{harvnb|Daly|2009|pp=227–228}} |2={{harvnb|Van Inwagen|2023}} }}</ref>{{efn|Although commonly labelled ''Plato's theory of forms'', there is some [[Socratic problem|scholarly disagreement]] about the extent to which this position belongs to [[Socrates]] rather than Plato.<ref>{{multiref | {{harvnb|Gerson|2002|p=[https://books.google.com/books?id=vbtbQk_A0YoC&pg=PA87 87]}} | {{harvnb|Dancy|2004|p=[https://books.google.com/books?id=WAoOQnoRa9gC&pg=PA11 11]}} }}</ref>}}

Another key concern in metaphysics is the division of entities into distinct groups based on underlying features they share. Theories of categories provide a system of the most fundamental kinds or the highest genera of being by establishing a comprehensive inventory of everything.<ref>{{multiref | {{harvnb|Thomasson|2022|loc=Lead Section}} | {{harvnb|Loux|Crisp|2017|pp=11–12}} | {{harvnb|Wardy|1998|loc=Lead Section}} }}</ref> One of the earliest theories of categories was proposed by Aristotle, who outlined a [[Categories_(Aristotle)#The_praedicamenta|system of 10 categories]]. He argued that [[Substance theory|substances]] (e.g., man and horse), are the most important category since all other categories like [[quantity]] (e.g., four), [[Quality (philosophy)|quality]] (e.g., white), and place (e.g., in Athens) are said of substances and depend on them.<ref>{{multiref | {{harvnb|Thomasson|2022|loc=§ 1.1 Aristotelian Realism}} | {{harvnb|Studtmann|2024|loc=§ 2. The Ten-Fold Division}} | {{harvnb|Wardy|1998|loc=§ 1. Categories in Aristotle}} }}</ref> Kant understood categories as fundamental principles underlying human understanding and developed a [[Category (Kant)|system of 12 categories]], divided into the four classes: quantity, quality, relation, and modality.<ref>{{multiref | {{harvnb|Thomasson|2022|loc=§ 1.2 Kantian Conceptualism}} | {{harvnb|Wardy|1998|loc=§ 1. Categories in Kant}} }}</ref> More recent theories of categories were proposed by [[Charles Sanders Peirce|C. S. Peirce]], [[Edmund Husserl]], [[Samuel Alexander]], [[Roderick Chisholm]], and [[E. J. Lowe (philosopher)|E. J. Lowe]].<ref>{{multiref | {{harvnb|Thomasson|2022|loc=§ 1.3 Husserlian Descriptivism, § 1.4 Contemporary Category Systems}} | {{harvnb|Grim|Rescher|2023|p=[https://books.google.com/books?id=KgPPEAAAQBAJ&pg=PT39 39]}} }}</ref> Many philosophers rely on the contrast between [[Abstract and concrete|concrete and abstract objects]]. According to a common view, concrete objects, like rocks, trees, and human beings, exist in space and time, undergo changes, and impact each other as cause and effect. They contrast with abstract objects, like [[number]]s and [[Set (mathematics)|sets]], which do not exist in space and time, are immutable, and do not engage in causal relations.<ref>{{multiref | {{harvnb|Falguera|Martínez-Vidal|Rosen|2022|loc=Lead Section, § 1. Introduction, § 3.5 The Ways of Negation}} | {{harvnb|Erasmus|2018|p=[https://books.google.com/books?id=ze5FDwAAQBAJ&pg=PA93 93]}} }}</ref>

=== Particulars ===
[[Particular]]s are individual entities and include both concrete objects, like Aristotle, the Eiffel Tower, or a specific apple, and abstract objects, like the number 2 or a specific set in mathematics. They are unique, non-repeatable entities and contrast with [[Universal (metaphysics)|universals]], like the color red, which can at the same time exist in several places and characterize several particulars.<ref>{{multiref | {{harvnb|Lowe|2005|p=683}} | {{harvnb|MacLeod|Rubenstein|loc=Lead Section, § 1a. The Nature of Universals}} | {{harvnb|Bigelow|1998|loc=Lead Section}} | {{harvnb|Campbell|2006|loc=§ Particularity and Individuality}} | {{harvnb|Maurin|2019|loc=Lead Section}} }}</ref> A widely held view is that particulars instantiate universals but are not themselves instantiated by something else, meaning that they exist in themselves while universals exist in something else. [[Substance theory|Substratum theory]], associated with [[John Locke]]'s philosophy, analyzes each particular as a substratum, also called ''bare particular'', together with various properties. The substratum confers individuality to the particular while the properties express its qualitative features or what it is like. This approach is rejected by [[Bundle theory|bundle theorists]]. Inspired by [[David Hume]]'s philosophy, they state that particulars are only bundles of properties without an underlying substratum. Some bundle theorists include in the bundle an individual essence, called ''[[haecceity]]'' following [[Scholasticism|scholastic]] terminology, to ensure that each bundle is unique. Another proposal for concrete particulars is that they are individuated by their space-time location.<ref>{{multiref | {{harvnb|Maurin|2019|loc=Lead Section}} | {{harvnb|Campbell|2006|loc=§ Particularity and Individuality}} | {{harvnb|Bigelow|1998|loc=Lead Section, § 3. Bundles of Properties}} | {{harvnb|Loux|Crisp|2017|pp=82–83}} }}</ref>

Concrete particulars encountered in everyday life, like rocks, tables, and organisms, are complex entities [[Composition (objects)|composed]] of various parts. For example, a table consists of a tabletop and legs, each of which is itself made up of countless particles. The relation between parts and wholes is studied by [[mereology]].<ref>{{multiref | {{harvnb|Loux|Crisp|2017|pp=250–251}} | {{harvnb|Varzi|2019|loc=Lead Section, § 1. 'Part' and Parthood}} | {{harvnb|Cornell|loc=Lead Section, § 2. The Special Composition Question}} | {{harvnb|Tallant|2017|pp=19–21}} }}</ref>{{efn|Mereological problems were discussed as early as ancient Greek philosophy.<ref>{{harvnb|Varzi|2019|loc=Lead Section}}</ref>}} The problem of the many is a philosophical question about the conditions under which several individual things compose a larger whole. For example, a cloud comprises many droplets without a clear boundary, raising the question of which droplets form part of the cloud. According to mereological universalists, every collection of entities forms a whole. This means that what seems to be a single cloud is an overlay of countless clouds, one for each cloud-like collection of water droplets. Mereological moderatists hold that certain conditions must be met for a group of entities to compose a whole, for example, that the entities touch one another. [[Mereological nihilism|Mereological nihilists]] reject the idea of wholes altogether, claiming that there are no clouds or tables but only particles that are arranged cloud-wise or table-wise.<ref>{{multiref | {{harvnb|Weatherson|2023|loc=Lead section, § 3. Overpopulation}} | {{harvnb|Loux|Crisp|2017|pp=82–83}} | {{harvnb|Cornell|loc=Lead Section, § 2. The Special Composition Question}} | {{harvnb|Brenner|2015|p=1295}} | {{harvnb|Tallant|2017|pp=19–21, 23–24, 32–33}} }}</ref> A related mereological problem is whether there are simple entities that have no parts, as [[Atomism|atomists]] claim, or whether everything can be endlessly subdivided into smaller parts, as continuum theorists contend.<ref>{{multiref | {{harvnb|Berryman|2022|loc=§ 2.6 Atomism and Particle Theories in Ancient Greek Sciences}} | {{harvnb|Varzi|2019|loc=§ 3.4 Atomism, Gunk, and Other Options}} }}</ref>

=== Universals ===
{{main|Universal (metaphysics)}}

Universals are general entities, encompassing both [[Property (philosophy)|properties]] and [[Relations (philosophy)|relations]], that express what particulars are like and how they resemble one another. They are repeatable, meaning that they are not limited to a unique existent but can be instantiated by different particulars at the same time. For example, the particulars [[Nelson Mandela]] and [[Mahatma Gandhi]] instantiate the universal {{em|humanity}}, similar to how a strawberry and a ruby instantiate the universal {{em|red}}.<ref>{{multiref | {{harvnb|MacLeod|Rubenstein|loc=Lead Section}} | {{harvnb|Bigelow|1998a|loc=Lead Section}} | {{harvnb|Cowling|2019|loc=Lead Section}} | {{harvnb|Loux|Crisp|2017|pp=17–19}} }}</ref>

A topic discussed since ancient philosophy, the [[problem of universals]] consists in the challenge of characterizing the ontological status of universals.<ref>{{multiref | {{harvnb|MacLeod|Rubenstein|loc=Lead Section, § 1c. The Problem of Universals}} | {{harvnb|Rodriguez-Pereyra|2000|pp=255–256}} | {{harvnb|Loux|Crisp|2017|pp=17–19}} }}</ref> Realists argue that universals are real, mind-independent entities that exist in addition to particulars. According to [[Theory of forms|Platonic realists]], universals exist independently of particulars, which implies that the universal {{em|red}} would continue to exist even if there were no red things. A more [[Aristotelianism#Problem of universals|moderate form of realism]], inspired by Aristotle, states that universals depend on particulars, meaning that they are only real if they are instantiated. [[Nominalism|Nominalists]] reject the idea that universals exist in either form. For them, the world is composed exclusively of particulars. [[Conceptualism|Conceptualists]] offer an intermediate position, stating that universals exist, but only as [[concept]]s in the mind used to order experience by classifying entities.<ref>{{multiref | {{harvnb|MacLeod|Rubenstein|loc=Lead Section, § 2. Versions of Realism, § 3. Versions of Anti-Realism}} | {{harvnb|Bigelow|1998a|loc=§ 4. Nominalism and Realism}} | {{harvnb|Loux|Crisp|2017|pp=17–19, 45}} }}</ref>{{efn|The positions of nominalism and conceptualism were formulated in medieval philosophy.<ref>{{harvnb|Hancock|2006|pp=188–190}}</ref>}}

[[Natural kind|Natural]] and social kinds are often understood as special types of universals. Entities belonging to the same natural kind share certain fundamental features characteristic of the structure of the natural world. In this regard, natural kinds are not an artificially constructed classification but are discovered,{{efn|The classified entities do not have to occur naturally and can encompass man-made products, such as synthetic chemical substances.<ref>{{multiref | {{harvnb|Brzović|loc=Lead Section}} | {{harvnb|Bird|Tobin|2024|loc=Lead Section}} }}</ref>}} usually by the natural sciences, and include kinds like [[electrons]], [[H2O|{{chem2|H2O}}]], and tigers. [[Scientific realism|Scientific realists]] and anti-realists disagree about whether natural kinds exist.<ref>{{multiref | {{harvnb|Brzović|loc=Lead Section, § 3. Metaphysics of Natural Kinds}} | {{harvnb|Bird|Tobin|2024|loc=Lead Section, § 1.2 Natural Kind Realism}} | {{harvnb|Liston|loc=Lead Section}} }}</ref> Social kinds, like [[money]] and [[baseball]],<ref>{{multiref | {{harvnb|Ásta|2017|pp=[https://www.taylorfrancis.com/chapters/edit/10.4324/9781315768571-27/social-kinds-%C3%A1sta 290–291]}} | {{harvnb|Bird|Tobin|2024|loc=§ 2.4 Natural Kinds and Social Science}} }}</ref> are studied by [[social metaphysics]] and characterized as useful social constructions that, while not purely fictional, do not reflect the fundamental structure of mind-independent reality.<ref>{{multiref| {{harvnb|Ney|2014|pp=259–263}}| {{harvnb|Rea|2021|pp=185–186}}}}</ref>

=== Possibility and necessity ===
The concepts of possibility and necessity convey what can or must be the case, expressed in modal statements like "it is possible to find a cure for cancer" and "it is necessary that two plus two equals four". Modal metaphysics studies metaphysical problems surrounding possibility and necessity, for instance, why some modal statements are true while others are false.<ref>{{multiref | {{harvnb|Parent|loc=Lead Section}} | {{harvnb|Loux|Crisp|2017|pp=149–150}} | {{harvnb|Koons|Pickavance|2015|pp=154–155}} | {{harvnb|Mumford|2012|loc=§ 8. What Is Possible?}} }}</ref>{{efn|A further topic concerns different types of modality, such as the contrast between physical, metaphysical, and logical necessity based on whether the necessity has its source in the [[Scientific law|laws of nature]], the essences of things, or the laws of logic.<ref>{{multiref | {{harvnb|Hanna|2009|p=[https://books.google.com/books?id=ka9BhOL1ev8C&pg=PA196 196]}} | {{harvnb|Hale|2020|p=[https://books.google.com/books?id=OSvsDwAAQBAJ&pg=PA142 142]}} }}</ref>}} Some metaphysicians hold that modality is a fundamental aspect of reality, meaning that besides facts about what is the case, there are additional facts about what could or must be the case.<ref>{{multiref | {{harvnb|Goswick|2018|pp=97–98}} | {{harvnb|Wilsch|2017|pp=428–429, 446}} }}</ref> A different view argues that modal truths are not about an independent aspect of reality but can be reduced to non-modal characteristics, for example, to facts about what properties or linguistic descriptions are compatible with each other or to [[Fictionalism|fictional statements]].<ref>{{multiref | {{harvnb|Goswick|2018|pp=97–98}} | {{harvnb|Parent|loc=§ 3. Ersatzism, § 4. Fictionalism}} | {{harvnb|Wilsch|2017|pp=428–429}} }}</ref>

Borrowing a term from German philosopher [[Gottfried Wilhelm Leibniz]]'s [[theodicy]], many metaphysicians use the concept of [[possible world]]s to analyze the meaning and ontological ramifications of modal statements. A possible world is a complete and consistent way the totality of things could have been.<ref>{{multiref | {{harvnb|Menzel|2023|loc=Lead Section, § 1. Possible Worlds and Modal Logic}} | {{harvnb|Berto|Jago|2023|loc=Lead Section}} | {{harvnb|Pavel|1986|p=[https://books.google.com/books?id=OF7ZA54UpYYC&pg=PA50 50]}} | {{harvnb|Campbell|2006|loc=§ Possible Worlds}} }}</ref> For example, the [[dinosaurs]] were [[Cretaceous–Paleogene extinction event|wiped out]] in the actual world but there are possible worlds in which they are still alive.<ref>{{harvnb|Nuttall|2013|p=[https://books.google.com/books?id=luc-Hf_bEOIC&pg=PT135 135]}}</ref> According to possible world semantics, a statement is possibly true if it is true in at least one possible world, whereas it is necessarily true if it is true in all possible worlds.<ref>{{multiref | {{harvnb|Menzel|2023|loc=Lead Section, § 1. Possible Worlds and Modal Logic}} | {{harvnb|Kuhn|2010|p=[https://books.google.com/books?id=c_eYe6NVaDMC&pg=PA13 13]}} }}</ref> [[Modal realism|Modal realists]] argue that possible worlds exist as concrete entities in the same sense as the actual world, with the main difference being that the actual world is the world we live in while other possible worlds are inhabited by [[Counterpart theory|counterparts]]. This view is controversial and various alternatives have been suggested, for example, that possible worlds only exist as abstract objects or are similar to stories told in works of [[fiction]].<ref>{{multiref | {{harvnb|Parent|loc=Lead Section, § 2. Lewis' Realism, § 3. Ersatzism, § 4. Fictionalism}} | {{harvnb|Menzel|2023|loc=Lead Section, § 2. Three Philosophical Conceptions of Possible Worlds}} | {{harvnb|Campbell|2006|loc=§ Modal Realism}} }}</ref>

=== Space, time, and change ===
{{main|Philosophy of space and time}}

[[Space]] and [[time]] are dimensions that entities occupy. Spacetime realists state that space and time are fundamental aspects of reality and exist independently of the human mind. Spacetime idealists, by contrast, hold that space and time are constructs of the human mind, created to organize and make sense of reality.<ref>{{multiref | {{harvnb|Dainton|2010|pp=[https://www.cambridge.org/core/books/abs/time-and-space/spatial-antirealism/CE284C8D3088AF598998951618D4867D 245–246]}} | {{harvnb|Janiak|2022|loc=§ 4.2 Absolute/Relational Vs. Real/Ideal}} | {{harvnb|Pelczar|2015|p=[https://books.google.com/books?id=tkjTBgAAQBAJ&pg=PA115 115]}} }}</ref> Spacetime absolutism or substantivalism understands spacetime as a distinct object, with some metaphysicians conceptualizing it as a container that holds all other entities within it. [[Relationalism#Relationalism (theory of space and time)|Spacetime relationism]] sees spacetime not as an object but as a network of relations between objects, such as the spatial relation of {{em|being next to}} and the temporal relation of {{em|coming before}}.<ref>{{multiref | {{harvnb|Hoefer|Huggett|Read|2023|loc=Lead Section}} | {{harvnb|Benovsky|2016|pp=[https://books.google.com/books?id=4KHWCwAAQBAJ&pg=PA19 19–20]}} | {{harvnb|Romero|2018|p=[https://books.google.com/books?id=5wJ2DwAAQBAJ&pg=PA135 135]}} }}</ref>

In the metaphysics of time, an important contrast is between the [[A series and B series|A-series and the B-series]]. According to the A-series theory, the [[flow of time]] is real, meaning that events are categorized into the past, present, and future. The present continually moves forward in time and events that are in the present now will eventually change their status and lie in the past. From the perspective of the B-series theory, time is static, and events are ordered by the temporal relations earlier-than and later-than without any essential difference between past, present, and future.<ref>{{multiref | {{harvnb|Dyke|2002|p=[https://books.google.com/books?id=IxIlqbSWg4gC&pg=PA138 138]}} | {{harvnb|Koons|Pickavance|2015|pp=182–185}} | {{harvnb|Carroll|Markosian|2010|pp=160–161}} }}</ref> [[Eternalism (philosophy of time)|Eternalism]] holds that past, present, and future are equally real, whereas [[Presentism (philosophy of time)|presentism]] asserts that only entities in the present exist.<ref>{{multiref | {{harvnb|Carroll|Markosian|2010|pp=179–181}} | {{harvnb|Loux|Crisp|2017|pp=206, 214–215}} | {{harvnb|Romero|2018|p=[https://books.google.com/books?id=5wJ2DwAAQBAJ&pg=PA135 135]}} }}</ref>

Material objects persist through time and change in the process, like a tree that grows or loses leaves.<ref>{{multiref | {{harvnb|Miller|2018|loc=Lead Section}} | {{harvnb|Costa|loc=Lead Section}} | {{harvnb|Simons|2013|p=[https://books.google.com/books?id=ql27m77IveQC&pg=PA166 166]}} }}</ref> The main ways of conceptualizing persistence through time are [[endurantism]] and [[perdurantism]]. According to endurantism, material objects are three-dimensional entities that are wholly present at each moment. As they change, they gain or lose properties but otherwise remain the same. Perdurantists see material objects as four-dimensional entities that extend through time and are made up of different [[temporal parts]]. At each moment, only one part of the object is present, not the object as a whole. Change means that an earlier part is qualitatively different from a later part. For example, when a banana ripens, there is an unripe part followed by a ripe part.<ref>{{multiref | {{harvnb|Miller|2018|loc=Lead Section}} | {{harvnb|Costa|loc=Lead Section, § 1. Theories of Persistence}} | {{harvnb|Simons|2013|p=[https://books.google.com/books?id=ql27m77IveQC&pg=PA166 166]}} | {{harvnb|Hawley|2023|loc=3. Change and Temporal Parts}} }}</ref>

=== Causality ===
{{main|Causality}}

Causality is the relation between cause and effect whereby one entity produces or alters another entity.<ref>{{multiref | {{harvnb|Carroll|Markosian|2010|pp=20–22}} | {{harvnb|Tallant|2017|pp=218–219}} }}</ref> For instance, if a person bumps a glass and spills its contents then the bump is the cause and the spill is the effect.<ref>{{harvnb|Carroll|Markosian|2010|p=20}}</ref> Besides the single-case causation between particulars in this example, there is also general-case causation expressed in statements such as "smoking causes cancer".<ref>{{multiref | {{harvnb|Carroll|Markosian|2010|pp=21–22}} | {{harvnb|Williamson|2012|p=[https://books.google.com/books?id=yWWEIvNgUQ4C&pg=PA186 186]}} }}</ref> The term [[agent causation]] is used when people and their actions cause something.<ref>{{multiref | {{harvnb|Ney|2014|pp=219, 252–253}} | {{harvnb|Tallant|2017|pp=233–234}} }}</ref> Causation is usually interpreted deterministically, meaning that a cause always brings about its effect. However, some philosophers such as [[G. E. M. Anscombe]] have provided counterexamples to this idea.<ref>{{multiref|{{harvnb|Wiland|Driver|2022|loc=§ 3. Metaphysics}}|{{harvnb|Van Miltenburg|2022|pp=1, 6}}}}</ref> Such counterexamples have inspired the development of [[Probabilistic causation|probabilistic theories]], which claim that the cause merely increases the probability that the effect occurs. This view can explain that smoking causes cancer even though this does not happen in every single case.<ref>{{multiref | {{harvnb|Ney|2014|pp=228–231}} | {{harvnb|Williamson|2012|pp=[https://books.google.com/books?id=yWWEIvNgUQ4C&pg=PA185 185–186]}} }}</ref>

The [[Humeanism#Causality and necessity|regularity theory of causation]], inspired by [[David Hume]]'s philosophy, states that causation is nothing but a [[constant conjunction]] in which the mind apprehends that one phenomenon, like putting one's hand in a fire, is always followed by another phenomenon, like a feeling of pain.<ref>{{multiref | {{harvnb|Lorkowski|loc=Lead Section, § 2. Necessary Connections and Hume’s Two Definitions, § 4. Causal Reductionism}} | {{harvnb|Carroll|Markosian|2010|pp=24–25}} | {{harvnb|Tallant|2017|pp=220–221}} }}</ref> According to nomic regularity theories, regularities manifest as [[Scientific law|laws of nature]] studied by science.<ref>{{harvnb|Ney|2014|pp=223–224}}</ref> [[Counterfactual conditional|Counterfactual]] theories focus not on regularities but on how effects depend on their causes. They state that effects owe their existence to the cause and would not occur without them.<ref>{{multiref | {{harvnb|Carroll|Markosian|2010|p=26}} | {{harvnb|Tallant|2017|pp=221–222}} | {{harvnb|Ney|2014|pp=224–225}} }}</ref> According to primitivism, causation is a basic concept that cannot be analyzed in terms of non-causal concepts, such as regularities or dependence relations. One form of primitivism identifies causal powers inherent in entities as the underlying mechanism.<ref>{{multiref | {{harvnb|Ney|2014|pp=231–232}} | {{harvnb|Mumford|2009|pp=94–95}} | {{harvnb|Mumford|Anjum|2013}} | {{harvnb|Koons|Pickavance|2015|pp=63–64}} }}</ref> Eliminativists reject the above theories by holding that there is no causation.<ref>{{harvnb|Tallant|2017|pp=231–232}}</ref>

=== Mind and free will ===
{{main|Mind|Free will}}

[[File:Dualism-vs-Monism.png|thumb|right|upright=1.3|alt=Diagram of approaches to the mind–body problem. It shows dualism in the form of Cartesian dualism on the left side. It presents monism in the forms of physicalism, idealism, and neutral monism on the right side.|Different approaches toward resolving the mind–body problem<ref>{{harvnb|Kind|Stoljar|2023|loc=[https://books.google.com/books?id=_VC_EAAAQBAJ&pg=PT19 § Introduction]}}</ref>]]

Mind encompasses phenomena like [[thinking]], [[perceiving]], [[feeling]], and [[desiring]] as well as the underlying faculties responsible for these phenomena.<ref>{{harvnb|Morton|2005|p=[https://www.oxfordreference.com/display/10.1093/acref/9780199264797.001.0001/acref-9780199264797-e-1608?rskey=jqUtkA&result=1601 603]}}</ref> The [[mind–body problem]] is the challenge of clarifying the relation between physical and mental phenomena. According to [[Cartesian dualism]], minds and bodies are distinct substances. They causally interact with each other in various ways but can, at least in principle, exist on their own.<ref>{{multiref | {{harvnb|McLaughlin|1999|pp=684–685}} | {{harvnb|Kim|2005|p=608}} }}</ref> This view is rejected by [[Monism|monists]], who argue that reality is made up of only one kind. According to metaphysical [[idealism]], everything is mental or dependent on the mind, including physical objects, which may be understood as ideas or perceptions of conscious minds.{{efn|There are other forms of idealism that assert slightly different positions, such as [[transcendental idealism]] and [[absolute idealism]].<ref>{{multiref | {{harvnb|Alston|2018|p=[https://books.google.com/books?id=4JNlDwAAQBAJ&pg=PA97 97]}} | {{harvnb|Guyer|Horstmann|2023|loc=§ 1. Introduction}} }}</ref>}} Materialists, by contrast, state that all reality is at its core material. Some deny that mind exists but the more common approach is to explain mind in terms of certain aspects of matter, such as brain states, behavioral [[disposition]]s, or functional roles.<ref>{{multiref | {{harvnb|McLaughlin|1999|pp=685–691}} | {{harvnb|Kim|2005|p=608}} | {{harvnb|Ramsey|2022|loc=Lead Section}} | {{harvnb|Pradhan|2020|p=[https://books.google.com/books?id=tSz7DwAAQBAJ&pg=PA4 4]}} }}</ref> [[Neutral monism|Neutral monists]] argue that reality is fundamentally neither material nor mental and suggest that matter and mind are both derivative phenomena.<ref>{{multiref | {{harvnb|Stubenberg|Wishon|2023|loc=Lead Section; § 1.3 Mind and Matter Revisited}} | {{harvnb|Griffin|1998}} }}</ref> A key aspect of the mind–body problem is the [[hard problem of consciousness]] or how to explain that physical systems like brains can produce phenomenal consciousness.<ref>{{harvnb|Weisberg|loc=Lead Section, § 1. Stating the Problem}}</ref>

The status of free will as the ability of a person to choose their [[Action (philosophy)|actions]] is a central aspect of the mind–body problem.<ref>{{multiref | {{harvnb|Timpe|loc=Lead Section}} | {{harvnb|Olson|2001|loc=[https://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/mind-body-problem Mind–Body Problem]}} | {{harvnb|Armstrong|2018|p=[https://books.google.com/books?id=uf7EDwAAQBAJ&pg=PA94 94]}} }}</ref> Metaphysicians are interested in the relation between free will and [[causal determinism]]{{em dash}}the view that everything in the universe, including human behavior, is determined by preceding events and laws of nature. It is controversial whether causal determinism is true, and, if so, whether this would imply that there is no free will. According to [[incompatibilism]], free will cannot exist in a deterministic world since there is no true choice or control if everything is determined.{{efn|For example, the [[consequence argument]] by [[Peter van Inwagen]] says that people have no power over the future if everything is determined by the past together with the laws of nature.<ref>{{multiref | {{harvnb|Vihvelin|2022|loc=§ 5. Choice and the Consequence Argument}} | {{harvnb|Kane|2011|p=[https://books.google.com/books?id=bOdoAgAAQBAJ&pg=PA10 10]}} }}</ref>}} [[Hard determinists]] infer from this that there is no free will, whereas [[Libertarianism (metaphysics)|libertarians]] conclude that determinism must be false. [[Compatibilists]] offer a third perspective, arguing that determinism and free will do not exclude each other, for instance, because a person can still act in tune with their motivation and choices even if they are determined by other forces. Free will plays a key role in ethics regarding the [[moral responsibility]] people have for what they do.<ref>{{multiref | {{harvnb|O’Connor|Franklin|2022|loc=Lead Section, § 2. The Nature of Free Will}} | {{harvnb|Timpe|loc=Lead Section, § 1. Free Will, Free Action and Moral Responsibility, § 3. Free Will and Determinism}} | {{harvnb|Armstrong|2018|p=[https://books.google.com/books?id=uf7EDwAAQBAJ&pg=PA94 94]}} }}</ref>

=== Others ===
[[Identity (philosophy)|Identity]] is a relation that every entity has to itself as a form of sameness. It refers to numerical identity when the same entity is involved, as in the statement "the [[Phosphorus (morning star)|morning star]] is the [[Hesperus|evening star]]" (both are the planet [[Venus]]). In a slightly different sense, it encompasses qualitative identity, also called ''exact similarity'' and ''indiscernibility'', which occurs when two distinct entities are exactly alike, such as perfect identical twins.<ref>{{multiref | {{harvnb|Kirwan|2005|pp=417–418}} | {{harvnb|Noonan|Curtis|2022|loc=Lead Section}} }}</ref> The principle of the indiscernibility of identicals is widely accepted and holds that numerically identical entities exactly resemble one another. The converse principle, known as the [[identity of indiscernibles]] or Leibniz's Law, is more controversial and states that two entities are numerically identical if they exactly resemble one another.<ref>{{multiref | {{harvnb|Sleigh|2005|p=418}} | {{harvnb|Kirwan|2005|pp=417–418}} | {{harvnb|Noonan|Curtis|2022|loc=§ 2. The Logic of Identity}} }}</ref> Another distinction is between synchronic and diachronic identity. Synchronic identity relates an entity to itself at the same time, whereas diachronic identity is about the same entity at different times, as in statements like "the table I bought last year is the same as the table in my dining room now".<ref>{{multiref | {{harvnb|Gallois|2016|loc=§ 2.1 Diachronic and Synchronic Identity}} | {{harvnb|Noonan|Curtis|2022|loc=Lead Section, § 5. Identity Over Time}} }}</ref> [[Personal identity]] is a related topic in metaphysics that uses the term ''identity'' in a slightly different sense and concerns questions like what [[personhood]] is or what makes someone a person.<ref>{{multiref | {{harvnb|Noonan|Curtis|2022|loc=Lead Section}} | {{harvnb|Olson|2023|loc=Lead Section, § 1. The Problems of Personal Identity}} | {{harvnb|Korfmacher}} }}</ref>

Various contemporary metaphysicians rely on the concepts of [[truth]], [[truth-bearer]], and [[Truthmaker theory|truthmaker]] to conduct their inquiry.<ref>{{multiref | {{harvnb|Tallant|2017|pp=1–4}} | {{harvnb|Koons|Pickavance|2015|pp=15–17}} }}</ref> Truth is a property of being in accord with reality. Truth-bearers are entities that can be true or false, such as linguistic statements and mental representations. A truthmaker of a statement is the entity whose existence makes the statement true.<ref>{{multiref | {{harvnb|Lowe|2005a|p=926}} | {{harvnb|Tallant|2017|pp=1–4}} | {{harvnb|Koons|Pickavance|2015|pp=15–17}} | {{harvnb|Asay|2020|p=[https://books.google.com/books?id=nRXeDwAAQBAJ&pg=PA11 11]}} | {{harvnb|MacBride|2022}} }}</ref> For example, the fact that a tomato exists and that it is red acts as a truthmaker for the statement "a tomato is red".<ref>{{multiref | {{harvnb|Rodriguez-Pereyra|2006|pp=191–192}} | {{harvnb|Beebee|Dodd|2005|pp=[https://books.google.com/books?id=l24TDAAAQBAJ&pg=PA2 2–3]}} | {{harvnb|Tallant|2017|p=1}} }}</ref> Based on this observation, it is possible to pursue metaphysical research by asking what the truthmakers of statements are, with different areas of metaphysics being dedicated to different types of statements. According to this view, modal metaphysics asks what makes statements about what is possible and necessary true while the metaphysics of time is interested in the truthmakers of temporal statements about the past, present, and future.<ref>{{multiref | {{harvnb|Tallant|2017|pp=1–4, 163–165}} | {{harvnb|Koons|Pickavance|2015|pp=15–17, 154}} | {{harvnb|Meinertsen|2018|pp=[https://books.google.com/books?id=8HiQDwAAQBAJ&pg=PA21 21–22]}} }}</ref> A closely related topic concerns the nature of truth. Theories of truth aim to determine this nature and include [[Correspondence theory of truth|correspondence]], [[Coherence theory of truth|coherence]], [[Pragmatic theory of truth|pragmatic]], [[Semantic theory of truth|semantic]], and [[Deflationary theory of truth|deflationary theories]].<ref>{{multiref | {{harvnb|Dowden|Swartz|loc=Lead section}} | {{harvnb|Engel|2014|pp=12, 34–35, 47}} }}</ref>