Metaphysics Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! === Possibility and necessity === The concepts of possibility and necessity convey what can or must be the case, expressed in statements like "it is possible to find a cure for cancer" and "it is necessary that two plus two equals four". They belong to modal metaphysics, which investigates the metaphysical principles underlying them, in particular, why it is the case that 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> Following [[Gottfried Wilhelm Leibniz]], 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 of how 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 while 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 that they 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> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here. You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see Christianpedia:Copyrights for details). Do not submit copyrighted work without permission! Cancel Editing help (opens in new window) Discuss this page