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Single Idea 12203

[filed under theme 10. Modality / E. Possible worlds / 1. Possible Worlds / e. Against possible worlds ]

Full Idea

A world is usually taken to be a fully determinate way that things could have been; but then one might seriously wonder whether anyone is capable of 'considering' such a thing at all.

Gist of Idea

If a world is a fully determinate way things could have been, can anyone consider such a thing?

Source

Ian Rumfitt (Logical Necessity [2010], §4)

Book Ref

'Modality', ed/tr. Hale,B/Hoffman,A [OUP 2010], p.60


A Reaction

This has always worried me. If I say 'maybe my coat is in the car', I would hate to think that I had to be contemplating some entire possible world (including all the implications of my coat not being on the hat stand).


The 11 ideas from 'Logical Necessity'

A distinctive type of necessity is found in logical consequence [Rumfitt, by Hale/Hoffmann,A]
Logical necessity is when 'necessarily A' implies 'not-A is contradictory' [Rumfitt]
Contradictions include 'This is red and not coloured', as well as the formal 'B and not-B' [Rumfitt]
Soundness in argument varies with context, and may be achieved very informally indeed [Rumfitt]
Geometrical axioms in logic are nowadays replaced by inference rules (which imply the logical truths) [Rumfitt]
There is a modal element in consequence, in assessing reasoning from suppositions [Rumfitt]
We reject deductions by bad consequence, so logical consequence can't be deduction [Rumfitt]
A logically necessary statement need not be a priori, as it could be unknowable [Rumfitt]
Narrow non-modal logical necessity may be metaphysical, but real logical necessity is not [Rumfitt]
If a world is a fully determinate way things could have been, can anyone consider such a thing? [Rumfitt]
The logic of metaphysical necessity is S5 [Rumfitt]