Page "Supervenience" Paragraph 3

Though it is intuitively clear what supervenience is, formally specifying what it means involves a complex technical apparatus and a family of related but subtly different definitions.

Most definitions involve comparisons of objects for indiscernibility.

According to one standard definition, a set of properties A ( e. g. mental properties ) supervenes on a set of properties B ( e. g. neural properties ), if and only if any two objects x and y which share all properties in B ( are " B-indiscernible ") must also share all properties in A ( are " A-indiscernible ").

The intuitive idea is that if you could make a physical copy of a person, you'd also be making a psychological copy of that person.

The reverse does not hold: two people could be in the same mental state, but that mental state could be supported by different brain states ( the same mental state could be " multiply realizable " by different brain states ).

The properties in B are called the base properties ( or sometimes subjacent or subvenient properties ), and the properties in A are called the supervenient properties.