Editing Metaphysics (section)

=== 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>