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Single Idea 5734

[filed under theme 10. Modality / E. Possible worlds / 1. Possible Worlds / a. Possible worlds ]

Full Idea

In modal logic the concepts of necessity and counterfactuals are not interdefinable, so the language needs two primitives to represent them, but with the machinery of possible worlds they are defined by what is the case in all worlds, or close worlds.

Clarification

'Primitives' are terms defined as basic, which cannot be analysed

Gist of Idea

Possible worlds make it possible to define necessity and counterfactuals without new primitives

Source

Joseph Melia (Modality [2003], Ch.1)

Book Ref

Melia,Joseph: 'Modality' [Acumen 2003], p.19

A Reaction

If your motivation is to reduce ontology to the barest of minimums (which it was for David Lewis) then it is paradoxical that the existence of possible worlds may be the way to achieve it. I doubt, though, whether a commitment to their reality is needed.

The 32 ideas with the same theme [existence of non-actual possible worlds]:

19402 The actual universe is the richest composite of what is possible [Leibniz]
19434 There may be a world where dogs smell their game at a thousand leagues [Leibniz]
15883 Leibniz narrows down God's options to one, by non-contradiction, sufficient reason, indiscernibles, compossibility [Leibniz, by Harré]
18822 Each monad expresses all its compatible monads; a possible world is the resulting equivalence class [Leibniz, by Rumfitt]
7837 Leibniz proposed possible worlds, because they might be evil, where God would not create evil things [Leibniz, by Stewart,M]
14460 If something is true in all possible worlds then it is logically necessary [Russell]
5400 In any possible world we feel that two and two would be four [Russell]
23470 Each thing is in a space of possible facts [Wittgenstein]
11183 The use of possible worlds is to sort properties (not to individuate objects) [Marcus (Barcan)]
16957 Possible worlds aren't how the world might be, but how a world might be, given some possibility [Dummett]
14662 Possible worlds clarify possibility, propositions, properties, sets, counterfacts, time, determinism etc. [Plantinga]
4943 Instead of talking about possible worlds, we can always say "It is possible that.." [Kripke]
11984 Asserting a possible property is to say it would have had the property if that world had been actual [Plantinga]
4899 Possible worlds thinking has clarified the logic of modality, but is problematic in epistemology [Perry]
16429 A 'centred' world is an ordered triple of world, individual and time [Stalnaker]
16397 If it might be true, it might be true in particular ways, and possible worlds describe such ways [Stalnaker]
16398 Possible worlds allow discussion of modality without controversial modal auxiliaries [Stalnaker]
16399 Possible worlds are ontologically neutral, but a commitment to possibilities remains [Stalnaker]
9669 There are no free-floating possibilia; they have mates in a world, giving them extrinsic properties [Lewis]
7691 The actual world is a consistent combination of states, made of consistent property combinations [Jacquette]
10266 Why does the 'myth' of possible worlds produce correct modal logic? [Shapiro]
4207 We might eliminate 'possible' and 'necessary' in favour of quantification over possible worlds [Lowe]
19279 What are these worlds, that being true in all of them makes something necessary? [Hale]
10983 Knowledge of possible worlds is not causal, but is an ontology entailed by semantics [Read]
7792 A world has 'access' to a world it generates, which is important in possible worlds semantics [Girle]
5734 Possible worlds make it possible to define necessity and counterfactuals without new primitives [Melia]
5742 In possible worlds semantics the modal operators are treated as quantifiers [Melia]
5743 If possible worlds semantics is not realist about possible worlds, logic becomes merely formal [Melia]
5749 Possible worlds could be real as mathematics, propositions, properties, or like books [Melia]
18745 A Tarskian model can be seen as a possible state of affairs [Horsten/Pettigrew]
18747 The 'spheres model' was added to possible worlds, to cope with counterfactuals [Horsten/Pettigrew]
17956 Closeness of worlds should be determined by the intrinsic nature of relevant objects [Vetter]