Causation as Constraint Propagation: A Structural Account Beyond Counterfactuals and Mechanisms

Contemporary theories of causation rely on counterfactual dependence, interventionist manipulability, or mechanistic organization, each capturing important aspects of causal explanation while leaving unresolved tensions concerning ontological grounding. Scientific practice nevertheless identifies stable causal structure across diverse domains, yet existing accounts struggle to integrate causal dependence, mechanism, and invariance without either inflating metaphysical commitments or fragmenting causal theory across incompatible frameworks. What remains lacking is a unified ontological account explaining why these diverse causal models converge in practice without invoking primitive causal relations, metaphysical necessity, or domain-specific ontologies. This paper develops a structural account of causation grounded in the Three-Circle Ontology, according to which causal relations are understood as constraint propagation within structured possibility spaces rather than as metaphysical connections between events. The account clarifies how counterfactual sensitivity, intervention stability, and mechanistic organization track different aspects of the same underlying structural dependencies. The paper does not propose a semantic theory of causation, replace interventionist methodology, or advance a mechanistic ontology. Its primary contribution is to reframe causation as structural constraint propagation, thereby unifying dominant causal frameworks while maintaining ontological economy.