Editing Metaphysics (section)

=== 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>