From Modal Proliferation to Glueability: Effective OSR and the Saatsi-Worry Extension

Effective ontic structural realism (effective OSR) offers a natural response to Saatsi’s worry about overly permissive effective realism by shifting primary realist commitment away from effective entities and toward modal structure. This paper argues that this shift leaves a further diagnostic pressure. If causal structure belongs within the modal commitments of effective OSR, then distinct effective descriptions of one and the same phenomenal situation may appear to support different causal-modal profiles. The worry is no longer simply one of too many effective entities, but of too many modal profiles for a single phenomenal target. I call this pressure the Saatsi-worry extension. I develop Modal Glueability (MG) as a conditional response. MG does not identify a formal structure with the world’s modal structure, nor does it attempt to establish the full ontic thesis of OSR. Instead, it asks whether the organisation of admissibility across controlled contextual variation is strong enough to support a unified-regime reading. This places MG between a structural-empiricist record of context-relative adequacy and an OSR-style identification claim. The paper’s main result, a Coherence-to-Glueability Theorem for the two-label case, gives a sufficient-condition route from coherent comparison to glueability. Its significance lies in showing how a baseline-anchored, phenomena-level comparison can discipline modal-profile variation without presupposing a successor story or a privileged theoretical formulation. In this sense, MG provides a conditional, non-identificatory response to the Saatsi-worry extension and specifies a diagnostic task for effective OSR once modal structure, rather than effective entities, becomes the realist focus.