Supervenience is a type of dependent relationship between properties of objects in philosophy.
In a supervenient relationship, if some set of properties, A, supervenes on some other set of properties, B, then changes in the properties of A will neccessarily result in a change of properties in B.
The relationship of supervenience is asymmetric — that is, if set A supervenes on set B, it is not the case that set B supervenes on set A.
In a supervenience relationship where set A supervenes on set B, the properties of set A are said to be the supervenient properties, while the properties of set B are said to be the subvenient properties. The subvenient properties are sometimes called base properties, basal properties or subjacent properties.
A classic non-philosophical example of a supervenience relationship has to do with the arrangement of matter. We tend to view objects with respect to their macroscopic properties — judging an object, such as a table, in terms of its shape, solidity, perceieved heat and its apparent colour. All of these properties are representative of other properties in the object, such as the arrangement of molecules, the strength of their bonds, their movement, and the electromagnetic energy they absorb and reflect.
Thus, it can be said that the macroscopic properties of the object with which we are familiar supervene on the microscopic properties of the object. If the microscopic (subvenient or base) properties changed, at the level of atoms and molecules — if they began to move faster or slower, for example — then there would be changes in the macroscopic (supervenient) properties of the larger physical object — it would heat up or cool down.
In aesthetics, the beauty of art is another example of a supervenience relationship. The beauty or aesthetic value of a painting, for example, is said to supervene on the physical properties of the painting.
Thus, if the physical properties of the painting changed, either by removing part of the painting, adding new brushstrokes, or changing its colours, then the beauty of the painting would change. It would become more or less beautiful as a direct result of the physical changes.
In the philosophy of mind, supervenience is also used to explain a proposed relationship between the mind and body — between the mental and physical properties of the brain. It is said that mental properties supervene on physical properties, and that mental states are caused by changes in brain states, but not vice-versa.
This also has the implication that two people with the same physical brain states would therefore share the same mental states.