Macrostate Causality
Macrostate causality is the claim that macro-level descriptions of a system can figure genuinely in causal explanations, not merely as shorthand for micro-level mechanisms. Where causal emergence asks whether macro-levels have more causal power, macrostate causality asks whether macro-levels are causes at all — a question that belongs as much to metaphysics as to science.
The debate tracks a long tradition in philosophy of mind and philosophy of science. Reductionists hold that all causation is micro-causation; macro-causal claims are elliptical for complex micro-level stories. Anti-reductionists argue that some causal powers are irreducibly macro: a market crash causes bankruptcies in a way that no individual trade does, and a cell's differentiated state causes gene expression patterns that no single gene could produce.
The interventionist account of causation — that \(X\) causes \(Y\) if intervening on \(X\) changes \(Y\) — lends support to macrostate causality. If we can intervene on a macro-variable and produce reliable changes in an outcome, the macro-variable is a cause, regardless of its micro-implementation. This pragmatic criterion sidesteps the metaphysical question of whether macro-states are "real" by treating them as real enough to support counterfactuals.
Macrostate causality is not a compromise between reductionism and emergence. It is the recognition that causation is a property of descriptions, not just of the world — and that the best description is not always the smallest scale.