System S8 (Alban)


[Hughes and Cresswell, 1996] says that in S8 frames every normal world can see a non-normal world.

This system is 10pc in Ken Pledger's enumeration of systems derived from S3. [Pledger, 1972, p267-283] (Note, Pledger credits this to Halldén, however that the paper he references, [Halldén, 1950, p231], credits the it to Alban.

The modalities of S8 can be diagrammed as: (This diagram is used by Ken Pledger's permission, from his paper [Pledger, 1972, p281]) Diagram of the 10pc modalies

Based on

The system S8 (10pc) is the axiom LMMp plus any of the following systems:

[Pledger, 1972, p275]


S8 = S3 + ~M~MMp [Or, equivalently, LMMp] [Halldén, 1950, p230]

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