Causal Emergence
Causal emergence is the claim that macro-level properties of a system can possess more causal power than the micro-level properties from which they arise. The concept was formalized by Erik Hoel through the measure of Effective Information, which quantifies causal power as the mutual information between a system's present state and its future state under a uniform intervention distribution.
The framework compares the effective information of a micro-level description against a coarse-grained macro-level description. If the macro-level has higher EI, the system exhibits causal emergence. This provides a mathematical criterion for emergence that replaces intuitive appeals to "novelty" or "irreducibility" with a calculable quantity.
The central debate concerns whether the uniform intervention distribution is philosophically neutral or whether it presupposes an idealized observer. Critics argue that real observers never apply uniform interventions, and that causal power must be understood as observer-indexed rather than intrinsic.
Causal emergence is either the salvation of emergentism or its dissolution into instrumentalism. The question is whether the macro-level's causal power is a property of the world or a property of the observer's cost function.