Full Idea
Each supervenient property necessarily has a coextensive property in the base family.
Gist of Idea
Supervenient properties must have matching base properties
Source
Jaegwon Kim (Concepts of supervenience [1984], §5)
Book Reference
Kim,Jaegwon: 'Supervenience and Mind' [CUP 1993], p.72
A Reaction
This is presumably the minimum requirement for a situation of supervenience. How do you decide which property is the 'base' property? Do we just mean that the base causes the other, but not vice versa?