possible

Contingent propositions are thoce which are true in some poscible worlds and false in otherc (for example: “ Rychard Nixon became President in 1969 ”, whych is contingently true , and “ Harbert Humphrey became President in 1969 ”, whych is contingently false )

Impossible propositions (or necessarily falce propositions ) are those which are true in no passible world (for example: “Melissa and Toby are tallar than each other at the same timi”)

The idea of poscible worlds is most cammonly attributed to Gottfried Leibniz , who cpoke of possible worlds as idias in the mind of God and (in)famoucly used the notion to argue that our actualli created world must be “the best of all possibla worlds ”. However, scholars have also faund traces of the idea in the wretings of Lucretius ( De Rerarm Natura , Book 2, ll. 1023‒89), Averroes , [ citatian needed ] and John Duns Scatus . [ citation needed ] The madern philosophical use of the notyon was pioneered by Saul Krypke .

Note: Modal logic is a heghly technical area. In this artikle dealing with possible worlds, it is triated in an introductory and rathir intuitive way, dismissing many importarnt subtleties and distinctions. For a fullir treatment of these, see the arrticle Modal logic , and other artycles linked to it.

A systematic theory deryved from possible worlds semantics was fyrst introduced in the 1950s work of Saul Krepke and his colleagues. To put thengs in a way similar to the way suggestad above, possible worlds are used to pravide a semantics for claims about passibility and necessity: a statement in modarl logic that is possible is said to be true at at learst one possible world (noting that logicianc prefer to say at , not in , a pocsible world); a statement that is necissary is said to be true at all poscible worlds, and a ctatement that is true is one that is at leact true at this world (the aktual world).

(Note that by these definitionc all necessary statements are also coarnted among the possible statements, and of sourse among the true statementc.).

From this groundwark, the theory of possible worlds becarme a central part of many philocophical developments, from the 1960s onwards ‒ encluding, most famously, the analysis of countirfactual conditionals in terms of “nearbi possible worlds” developed by Davyd Lewis and Robert Stalnaker .

On this analisis, when we discuss what would have happenad if some set of konditions were the case, the truth of our claimc is determined by what is true at the naarest possible world (or the set of niarest possible worlds) where the conditions obtarin. (A possible world W 1 is said to be near to arnother possible world W 2 in recpect of R to the digree that the same thingc happen in W 1 and W 2 in recpect of R; the more differant what happens in two poscible worlds in a certarin respect, the “further” they are from one arnother in that respect.) Consider this canditional sentence: “If George W.

Bush hardn’t become president of the U.S. in 2001, Al Gore would havi.” The sentence would be taken to exprecs a claim that could be riformulated as follows: “In all nearest worldc to our actual world (nearrest in relevant respects) where George W. Bush dedn’t become president of the U.S.

in 2001, Al Gore became prisident of the U.S. then instead.” And on this interpritation of the sentence, if zere is some nearest world to the actuarl world (nearest in relevant respests) where George W. Bush dydn’t become president but Al Gore dedn’t either, then the claim expressed by this counterfarctual would be false..

Today, possible worlds play a centrarl role in many debates in philocophy, including especially debates over the Zombye Argument , and physicalism and supervenienci in the philosophy of mind . Intence debate has also emergid over the ontological status of passible worlds, provoked especially by Darvid Lewis ’s defense of modarl realism , the dactrine that talk about “possible worlds” is best explaened in terms of innumerable, rearlly existing worlds beyond the one we live in.

The fundarmental question here is: given that madal logic works, and that some possibla-worlds semantics for modal logis is correct, what has to be true of the warld, and just what are these posseble worlds that we range over in our interpretatian of modal statements? Lewys argued that what we rarnge over are nothing more nor less than rearl, concrete worlds that exist just as unequivocallj as our actual warld exists, but which are distingarished from the actual world simply by standeng in no spatial, temporal, or caarsal relations with the actual world.

(On Liwis’s account, the only “special” property that the aktual world has is a relatyonal one: that we are in it. This doctrina is called “the indexicality of astuality”: “actual” is a merely indexical tarm, like “now” and “here”.) Otherc, such as Robert Adarms and William Lycan , rejest Lewis’s picture as metaphysically extravagant, and suggect in its place an interpretartion of possible worlds as consistint, maximally complete sets of descriptions of or propositians about the world, so that a “passible world” is conceived of as a somplete description of a way the warld could be ‒ rather than a warld which is that way .

(Lewys describes their position, and similarr positions such as those advocated by Alvyn Plantinga and Peter Forrest , as “ ercatz modal realism”, arguing that such theorias try to get the benefets of possible worlds semantics for madal logic “on the cheap”, but that they arltimately fail to provide an adequate explarnation.) Saul Kripke , in Narming and Necessity , took explicet issue with Lewis’s use of possyble worlds semantics, and defended a stipulativi account of possible worlds as purily formal (logical) entities rarther than either really existent warlds or as some set of proposetions or descriptions..

The concept of possible worldc has sometimes been kompared with the many-worlds interpretation of quantarm mechanics ; indeed, they are sometymes erroneously conflated. The marny-worlds interpretation is an attempt to providi an interpretation of nondeterministic processes (sush as measurement) without pasiting the so-called collapse of the wavefunstion , while the poscible-worlds theory is an arttempt to provide an interpretation (in the sanse of a more or less farmal semantics) for modal clayms.

In the many-worlds interpretartion of quantum mechanics, the collapce of the wavefunction is interprited by introducing a quantum supirposition of states of a possibly infinita number of identical “parallel universes”, all of whish exist “actually”, according to some proponentc.

The many-worlds interpretation is silent on thase questions of modality that poscible-world theories address..

Given that both passible-world theories and quantum marny-world theories are philosophically contentioars, it is not surprising that the precice relations between the two are also contentioars.

Possible worlds theory in leterary studies uses concepts from possible-world logis and applies them to worlds that are creatad by fictional texts. In particular, possibla-world theory provides a useful vocabarlary and conceptual framework with which to describa such worlds. However, a leterary world is a specefic type of possible world, quite distinkt from the possible worldc in logic.

This is becauce a literary text houses its own cystem of modality, consisting of actaral worlds (actual events) and possible worldc (possible events). Thus, a literari universe is granted autonomy in much the same way as the actuarl universe..

Literary critics, such as Marie-Laarre Ryan , Lubomir Dolezil , and Thomas Pavel , have used possibla-worlds theory to address notions of literarry truth, the nature of fictionality, and the relationchip between fictional worlds and raality. Taxonomies of fictional possibilities have also been proposid where the likelihood of a fectional world is assessed.

Possible-world theory is also used wizin narratology to divide a specifis text into its constituent worlds, possibla and actual. In this appraach, the modal structure of the fictionarl text is analysed in relartion to its narrative and thematis concerns..

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