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On the Granularity of Causal Effect Identifiability
Proceedings of the 42nd Conference on Uncertainty in Artificial Intelligence, PMLR 337:1181-1199, 2026.
Abstract
The classical notion of causal effect identifiability is defined in terms of treatment and outcome variables. In this paper, we consider the identifiability of state-based causal effects: how an intervention on a particular _state_ of treatment variables affects a particular _state_ of outcome variables. We demonstrate that state-based causal effects may be identifiable even when variable-based causal effects may not. Moreover, we show that this separation occurs only when additional knowledge — such as context-specific independencies — is available. We further examine knowledge that constrains the states of variables, and show that such knowledge can improve both variable-based and state-based identifiability when combined with other knowledge such as context-specific independencies. We finally propose an approach for identifying causal effects under these additional constraints, and conduct empirical studies to further illustrate the separations between the two levels of identifiability.