Supervening

Supervening is a term used in philosophy and law to describe a dependency relation between levels of description or sets of properties. In philosophy, a property A is said to supervene on a set of properties B if any difference in A requires a difference in B, while two entities sharing the same B-properties cannot differ in A. The phrase historically derives from Latin supervenire, "to come upon" or "to rise on top of."

Philosophical use emphasizes that higher-level properties depend on lower-level ones without necessarily being reducible to them. There are variations such as strong versus weak supervenience, and global versus local supervenience. The concept accommodates multiple realizability, in which the same higher-level property can be instantiated by different lower-level configurations, provided the relevant base properties align. Common examples include mental states supervening on brain states, and ethical properties supervening on physical states of agents.

In law, supervening (or a supervening event or supervening cause) refers to an event that occurs after a defendant's act and alters the outcome, potentially breaking the chain of causation. Courts evaluate whether the event is independent, unforeseeable, and sufficiently proximate to the harm. Examples include an unexpected natural disaster or an intervening criminal act. The doctrine aims to separate liability when a later factor overrides the original act.

Relation to reduction: supervenience does not require reduction. A can change only if B changes, but A need not be reducible to B; multiple realizations of A are possible in philosophy of mind and metaphysics.