more from this thinker     |     more from this text

Single Idea 19032

[filed under theme 4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / h. System S5 ]

Full Idea

Wedgwood (2007:220) argues that S5 is undesirable because it excludes that necessary truths may have contingent grounds.

Gist of Idea

S5 is undesirable, as it prevents necessities from having contingent grounds

Source

Barbara Vetter (Potentiality [2015], 6.4 n5)

Book Ref

Vetter,Barbara: 'Potentiality: from Dispositions to Modality' [OUP 2015], p.213

A Reaction

Cameron defends the possibility of necessity grounded in contingency, against Blackburn's denial of it. It's interesting that we choose the logic on the basis of the metaphysics. Shouldn't there be internal reasons for a logic's correctness?

Related Ideas

Idea 14529 If something underlies a necessity, is that underlying thing necessary or contingent? [Blackburn, by Hale/Hoffmann,A]

Idea 15103 Blackburn fails to show that the necessary cannot be grounded in the contingent [Cameron]

The 18 ideas with the same theme [strongest system, with three accessibility conditions]:

7791 The simplest of the logics based on possible worlds is Lewis's S5 [Lewis,CI, by Girle]
14973 In S5 all the long complex modalities reduce to just three, and their negations [Cresswell]
13604 Real possibility and necessity has the logic of S5, which links equivalence classes of worlds of the same kind [Ellis]
14686 S5 modal logic ignores accessibility altogether [Salmon,N]
14691 S5 believers say that-things-might-have-been-that-way is essential to ways things might have been [Salmon,N]
14693 The unsatisfactory counterpart-theory allows the retention of S5 [Salmon,N]
14627 S4, and therefore S5, are invalid for metaphysical modality [Salmon,N, by Williamson]
9560 S5 provides the correct logic for necessity in the broadly logical sense [Fine,K]
9065 S5 collapses iterated modalities (◊□P→□P, and ◊◊P→◊P) [Keefe/Smith]
9748 System S5 has the 'reflexive', 'symmetric' and 'transitive' conditions on its accessibility relation [Fitting/Mendelsohn]
14626 In S5 matters of possibility and necessity are non-contingent [Williamson]
15131 If metaphysical possibility is not a contingent matter, then S5 seems to suit it best [Williamson]
13708 S5 is the strongest system, since it has the most valid formulas, because it is easy to be S5-valid [Sider]
7793 ◊p → □◊p is the hallmark of S5 [Girle]
7795 S5 has just six modalities, and all strings can be reduced to those [Girle]
18814 'Absolute necessity' would have to rest on S5 [Rumfitt]
12204 The logic of metaphysical necessity is S5 [Rumfitt]
19032 S5 is undesirable, as it prevents necessities from having contingent grounds [Vetter]