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Single Idea 14974

[filed under theme 8. Modes of Existence / A. Relations / 4. Formal Relations / a. Types of relation ]

Full Idea

A relation is 'Euclidean' if aRb and aRc imply bRc.

Gist of Idea

A relation is 'Euclidean' if aRb and aRc imply bRc

Source

Max J. Cresswell (Modal Logic [2001], 7.1.2)

Book Ref

'Blackwell Guide to Philosophical Logic', ed/tr. Goble,Lou [Blackwell 2001], p.141


A Reaction

If a thing has a relation to two separate things, then those two things will also have that relation between them. If I am in the same family as Jim and as Jill, then Jim and Jill are in the same family.


The 7 ideas from Max J. Cresswell

Normal system K has five axioms and rules [Cresswell]
D is valid on every serial frame, but not where there are dead ends [Cresswell]
S4 has 14 modalities, and always reduces to a maximum of three modal operators [Cresswell]
In S5 all the long complex modalities reduce to just three, and their negations [Cresswell]
A relation is 'Euclidean' if aRb and aRc imply bRc [Cresswell]
A de dicto necessity is true in all worlds, but not necessarily of the same thing in each world [Cresswell]
Reject the Barcan if quantifiers are confined to worlds, and different things exist in other worlds [Cresswell]