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{{About|the term in logic and philosophy}} |
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In [[logic]] and [[philosophy]], the term '''proposition''' i lick viginia |
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refers to either (a) the ''"content"'' or ''[[Meaning (philosophy of language)|"meaning"]]'' of a meaningful [[declarative sentence]] or (b) the pattern of [[symbol (formal)|symbols]], marks, or sounds that make up a meaningful declarative sentence. The meaning of a ''proposition'' includes having the quality or property of being either [[truth|true]] or [[falsity|false]], and as such propositions are claimed to be [[truthbearer]]s. |
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The existence of propositions in sense (a) above, as well as the existence of "meanings", is disputed by some philosophers. Where the concept of a "meaning" is admitted, its nature is controversial. In earlier texts writers have not always made it sufficiently clear whether they are using the term ''proposition'' in sense of the words or the "meaning" expressed by the words.<ref>see eg http://plato.stanford.edu/entries/propositions/</ref> To avoid the controversies and [[ontology|ontological]] implications, the term ''sentence'' is often now used instead of ''proposition'' to refer to just those strings of symbols that are truthbearers, being either true or false under an interpretation. Strawson advocated the use of the term [[Statement (logic)|"statement"]], and this is the current usage in mathematical logic.{{Citation needed|date=November 2010}} |
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==Historical usage== |
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===Usage in Aristotle=== |
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[[Aristotelian logic]] identifies a proposition as a sentence which affirms or denies a [[Predicate (logic)|predicate]] of a [[Subject (grammar)|subject]]. An Aristotelian proposition may take the form "All men are mortal" or "Socrates is a man." In the first example the subject is "men" and the predicate "are mortal". In the second example the subject is "Socrates" and the predicate is "is a man". |
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===Usage by the logical positivists=== |
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Often propositions are related to [[Sentence (mathematical logic)|closed sentences]] to distinguish them from what is expressed by an [[open sentence]]. In this sense, propositions are "statements" that are [[Truthbearer|truth bearers]]. This conception of a proposition was supported by the philosophical school of [[logical positivism]]. |
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Some philosophers argue that some (or all) kinds of speech or actions besides the declarative ones also have propositional content. For example, yes-no [[question]]s present propositions, being inquiries into the [[truth value]] of them. On the other hand, some [[Semiotics|sign]]s can be declarative assertions of propositions without forming a sentence nor even being linguistic, e.g. traffic signs convey definite meaning which is either true or false. |
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Propositions are also spoken of as the content of [[belief]]s and similar [[propositional attitude|intentional attitudes]] such as desires, preferences, and hopes. For example, "I desire ''that I have a new car''," or "I wonder ''whether it will snow''" (or, whether it is the case that "it will snow"). Desire, belief, and so on, are thus called propositional attitudes when they take this sort of content. |
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===Usage by Russell=== |
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[[Bertrand Russell]] held that propositions were structured entities with objects and properties as constituents. Wittgenstein held that a proposition is the set of possible worlds/states of affairs in which it is true. One important difference between these views is that on the Russellian account, two propositions that are true in all the same states of affairs can still be differentiated. For instance, the proposition that two plus two equals four is distinct on a Russellian account from three plus three equals six. If propositions are sets of possible worlds, however, then all mathematical truths are the same set (the set of all possible worlds). |
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==Relation to the mind== |
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In relation to the mind, propositions are discussed primarily as they fit into [[propositional attitudes]]. Propositional attitudes are simply attitudes characteristic of [[folk psychology]] (belief, desire, etc.) that one can take toward a proposition (e.g. 'it is raining', 'snow is white', etc.). In English, propositions usually follow folk psychological attitudes by a "that clause" (e.g. "Jane believes ''that'' it is raining"). In [[philosophy of mind]] and [[psychology]], mental states are often taken to primarily consist in propositional attitudes. The propositions are usually said to be the "mental content" of the attitude. For example, if Jane has a mental state of believing that it is raining, her mental content is the proposition 'it is raining'. Furthermore, since such mental states are ''about'' something (namely propositions), they are said to be [[intentionality|intentional]] mental states. Philosophical debates surrounding propositions as they relate to propositional attitudes have also recently centered on whether they are internal or external to the agent or whether they are mind-dependent or mind-independent entities (see the entry on [[Internalism#Philosophy of mind|internalism and externalism]] in philosophy of mind). |
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==Treatment in logic== |
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As noted above, in [[Aristotelian logic]] a proposition is a particular kind of sentence, one which affirms or denies a [[Predicate (logic)|predicate]] of a [[subject (philosophy)|subject]]. Aristotelian propositions take forms like "All men are mortal" and "Socrates is a man." |
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In [[mathematical logic]], propositions, also called "[[propositional formula]]s" or "statement forms", are [[statement (logic)|statement]]s that do not contain [[quantifier]]s. They are composed of [[well-formed formulas]] consisting entirely of [[atomic formula]]s, the five [[logical connective]]s, and symbols of grouping (parentheses etc.). [[Propositional calculus|Propositional logic]] is one of the few areas of [[mathematics]] that is totally solved, in the sense that it has been proven internally consistent, every theorem is true, and every true statement can be proved.<ref>A. G. Hamilton, ''Logic for Mathematicians'', Cambridge University Press, 1980, ISBN 0521292913</ref> (From this fact, and [[Gödel's Theorem]], it is easy to see that propositional logic is not sufficient to construct the set of integers.) The most common extension of [[propositional calculus|propositional logic]] is called [[predicate calculus|predicate logic]], which adds [[variable (math)|variable]]s and [[quantifier]]s. |
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==Objections to propositions== |
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Attempts to provide a workable definition of proposition include |
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<blockquote> |
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Two meaningful declarative sentences express the same proposition if and only if they mean the same thing. |
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</blockquote> |
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thus defining ''proposition'' in terms of synonymity. For example, "Snow is white" (in English) and "Schnee ist weiß" (in German) are different sentences, but they say the same thing, so they express the same proposition. |
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<blockquote> |
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Two meaningful declarative sentence-tokens express the same proposition if and only if they mean the same thing. |
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</blockquote> |
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Unfortunately, the above definition has the result that two sentences/sentence-tokens which have the same meaning and thus express the same proposition, could have different truth-values, e.g. "I am Spartacus" said by Spartacus and said by John Smith; and e.g. "It is Wednesday" said on a Wednesday and on a Thursday. |
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A number of philosophers and linguists claim that all definitions of a proposition are too vague to be useful. For them, it is just a misleading concept that should be removed from philosophy and [[semantics]]. [[W.V. Quine]] maintained that the indeterminacy of translation prevented any meaningful discussion of propositions, and that they should be discarded in favor of [[Sentence (mathematical logic)|sentences]].<ref>Quine W.V. ''Philosophy of Logic'', Prentice-Hall NJ USA: 1970, pp 1-14</ref> Strawson advocated the use of the term [[Statement (logic)|"statement"]]. |
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==Related concepts== |
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[[Fact]]s are verifiable information.{{Citation needed|date=November 2010}}<ref>http://plato.stanford.edu/entries/propositions/#nature</ref> Simple facts are often stated as propositions: "Apples are a type of fruit." The opposite statement—"Apples are not a type of fruit"—is still a properly formulated proposition, even though it is false (not a fact). Most statements of fact are [[compound fact]]s: e.g., that apples exist, that fruit exists, that there are multiple types of fruit, etc. |
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A [[premise]] is a proposition that is used as the foundation for drawing [[conclusions]]. For example: |
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* ''Premise'': "Apples are a type of fruit." |
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* ''Premise'': "All types of fruit are food." |
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* ''Conclusion'': "Therefore, apples are food." |
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If the conclusion is false then either one or more of the premisses is false or the process of combining the premises is [[Validity|logically invalid]]. If the premisses are true and the process is logically valid, then the conclusion must be true. |
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==See also== |
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{{Portal box|Philosophy|Logic}} |
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* [[Main contention]] |
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==References== |
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{{Reflist}} |
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==External links== |
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*[[Stanford Encyclopedia of Philosophy]] articles on: |
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**[http://plato.stanford.edu/entries/propositions/ Propositions], by Matthew McGrath |
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**[http://plato.stanford.edu/entries/propositions-singular/ Singular Propositions], by Greg Fitch |
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**[http://plato.stanford.edu/entries/propositions-structured/ Structured Propositions], by Jeffrey C. King |
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{{Logic}} |
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{{philosophy of language}} |
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[[Category:Semantic units]] |
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[[Category:Philosophy of language]] |
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[[Category:Statements]] |
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[[Category:Logical syntax]] |
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[[Category:Mental content]] |
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[[Category:Mathematical logic]] |
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[[Category:Propositional calculus]] |
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[[ar:افتراض]] |
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[[bg:Пропозиция]] |
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[[ca:Proposició]] |
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[[cs:Výrok (logika)]] |
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[[da:Udsagn]] |
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[[de:Aussage (Logik)]] |
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[[de:Proposition (Linguistik)]] |
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[[et:Propositsioon]] |
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[[es:Proposición]] |
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[[fa:گزاره (منطق)]] |
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[[gl:Proposición]] |
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[[ko:명제]] |
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[[hy:Դատողություն]] |
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[[io:Propoziciono]] |
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[[it:Proposizione (logica)]] |
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[[he:טענה]] |
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[[nl:Propositie]] |
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[[ja:命題]] |
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[[nn:Proposisjon]] |
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[[pl:Sąd (logika)]] |
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[[pt:Proposição]] |
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[[ru:Суждение]] |
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[[simple:Proposition]] |
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[[sk:Výrok (logika)]] |
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[[ckb:پێشنیار]] |
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[[fi:Propositio]] |
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[[sv:Påstående]] |
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[[th:ประพจน์]] |
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[[uk:Судження]] |
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[[ur:مستلف]] |
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[[vi:Mệnh đề toán học]] |
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[[zh-yue:命題]] |
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[[zh:命题]] |
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