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Single Idea 13721

[filed under theme 10. Modality / A. Necessity / 3. Types of Necessity ]

Full Idea

'Strong necessity' requires the truth of 'necessarily φ' is all possible worlds. 'Weak necessity' merely requires that 'necessarily φ' be true in all worlds in which objects referred to within φ exist.

Gist of Idea

'Strong' necessity in all possible worlds; 'weak' necessity in the worlds where the relevant objects exist

Source

Theodore Sider (Logic for Philosophy [2010], 9.6.3)

Book Ref

Sider,Theodore: 'Logic for Philosophy' [OUP 2010], p.248

A Reaction

This seems to be a highly desirably distinction, given the problem of Idea 13719. It is weakly necessary that humans can't fly unaided, assuming we are referring the current feeble wingless species. That hardly seems to be strongly necessary.

Related Ideas

Idea 13719 Barcan Formula problem: there might have been a ghost, despite nothing existing which could be a ghost [Sider]

Idea 16466 Strong necessity is always true; weak necessity is cannot be false [Stalnaker]

The 26 ideas with the same theme [different ways in which things must be]:

1690 A stone travels upwards by a forced necessity, and downwards by natural necessity [Aristotle]
21389 Carneades distinguished logical from causal necessity, when talking of future events [Long on Carneades]
21362 Necessity is physical, logical, mathematical or moral [Schopenhauer, by Janaway]
9442 The only necessity is logical necessity [Wittgenstein]
13576 Necessities are distinguished by their grounds, not their different modalities [Ellis]
6987 We should not multiply senses of necessity beyond necessity [Jackson]
15291 There is 'absolute' necessity (implied by all propositions) and 'relative' necessity (from what is given) [Harré/Madden]
16466 Strong necessity is always true; weak necessity is cannot be false [Stalnaker]
14680 Logical possibility contains metaphysical possibility, which contains nomological possibility [Salmon,N]
9205 The three basic types of necessity are metaphysical, natural and normative [Fine,K]
15079 'Conceptual' necessity is narrow logical necessity, true because of concepts and logical laws [Lowe]
16533 Logical necessities, based on laws of logic, are a proper sub-class of metaphysical necessities [Lowe]
8261 Maybe not-p is logically possible, but p is metaphysically necessary, so the latter is not absolute [Hale]
15081 A strong necessity entails a weaker one, but not conversely; possibilities go the other way [Hale]
15080 'Relative' necessity is just a logical consequence of some statements ('strong' if they are all true) [Hale]
13721 'Strong' necessity in all possible worlds; 'weak' necessity in the worlds where the relevant objects exist [Sider]
19286 'Absolute necessity' is when there is no restriction on the things which necessitate p [Hale]
19288 Logical and metaphysical necessities differ in their vocabulary, and their underlying entities [Hale]
19290 Absolute necessities are necessarily necessary [Hale]
7800 Analytic truths are divided into logically and conceptually necessary [Girle]
4646 Is 'events have causes' analytic a priori, synthetic a posteriori, or synthetic a priori? [Baggini /Fosl]
9482 If the laws necessarily imply p, that doesn't give a new 'nomological' necessity [Bird]
13244 Relevant necessity is always true for some situation (not all situations) [Beall/Restall]
10933 Physical possibility is part of metaphysical possibility which is part of logical possibility [Rami]
14703 Superficial necessity is true in all worlds; deep necessity is thus true, no matter which world is actual [Schroeter]
14532 A distinctive type of necessity is found in logical consequence [Rumfitt, by Hale/Hoffmann,A]