Identifying causal effects from observational data typically requires a fully specified causal graph, an assumption that is often unrealistic in complex or high-dimensional settings. Causal abstractions address this limitation by retaining only partial causal information, thereby defining equivalence classes of compatible causal graphs. In this paper, we study causal effect identifiability directly at the level of these graph collections, rather than at the level of individual causal diagrams. We formalize several notions of identifiability in this setting and organize them into a hierarchy that clarifies their relationships and differences. In particular, we establish that a causal effect may be identified over a collection of graphs without admitting a single causal derivation that holds uniformly across all compatible graphs. These results help reveal gaps and clarify ambiguities in the existing literature.
Figures & tables
Figure 1: Hierarchy between the notions of identifiability. An arrow indicates that the implication holds in every case. A red cross on an arrow indicates that the implication fails in at least one case.
Figure 2: Derivation graph of the DAG from Example 2 . Blue nodes denote interventional queries, while orange nodes denote do-free queries. Edges of the derivation graph represent valid applications of the do-calculus rules in the DAG: gray solid lines for Rule R1 , orange dashed lines for Rule R2 , and blue dotted lines for Rule R3 . Only vertices that are non-isolated are displayed.
Appendix figures & tables3 assets
Supplementary material from the paper’s appendix.
Appendix
Figure 3: The Napkin Graph ( Pearl and Mackenzie, 2018 ; Guo et al., 2025 )
Figure 4: Intersection of the derivations graphs of G1 and G2 . Blue nodes denote interventional queries, while orange nodes denote do-free queries. Edges represent applications of the do-calculus rules: gray solid lines for Rule R1 , orange dashed lines for Rule R2 , and blue dotted lines for Rule R3 . Only non-isolated queries are displayed.
Figure 5: Derivation graph of G3 . Blue nodes denote interventional queries, while orange nodes denote do-free queries. Edges represent applications of the do-calculus rules: gray solid lines for Rule R1 , orange dashed lines for Rule R2 , and blue dotted lines for Rule R3 . Only non isolated queries are displayed.