# von Wright's 1951 Deontic Logic System.

[Hilpinen, 1981, pages 8-12]

## Notes

This system was published by Georg Henrik von Wright in 1951 in a paper
called "Deontic Logic" that appeared in "Mind".

This system uses a modality "O", where Op is taken as meaning p is
Obligitory.

This system uses a modality "P", where Pq is taken as meaning q is
Permissible.

He later published his Dyadic 1956 system
partly to overcome the weaknesses of this system.

He also published a Dyadic System in
1964

## Based on

- PC
- Axioms (Hilpinen calls these C1-5, but EVERYONE uses C1-5 for something different so:)
- vC1: Oq == ~P~q
- vC2: Pq + P~q
- vC3: P(q+r) == Pq + Pr
- vC4: O(q&~q) is not valid. ~P(q&~q) is not valid. (The principle of
deontic contingency)
- vC5: If q and r are logically equivalent, Pq and Pr are logicically
equivalent.

## Basis for

I'm not aware of any...

## Compare with

Deontic ("Standard")
Deontic (von Wright, 1956)
Deontic (von Wright, 1965)
Deontik (Mally)

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This page last updated October 14th, 2005