Applying qualitative comparative analysis (QCA) to large Ns relaxes researchers' case-based knowledge. This is problematic because causality in QCA is inferred from a dialogue between empirical, theoretical, and case-based knowledge. The lack of case-based knowledge may be remedied by various robustness tests. However, being a case-based method, QCA is designed to be sensitive to such tests, meaning that also large-"N" QCA robustness tests must be evaluated against substantive knowledge. This article connects QCA's substantive-interpretation approach of causality to critical realism. From that perspective, it identifies relevant robustness tests and applies them to a real-data large-"N" QCA study. Robustness test findings are visualized in a robustness table, and this article develops criteria to substantively interpret them. The robustness table is introduced as a tool to substantiate the validity of causal claims in large-"N" QCA studies.