 Spinoza is emphatic that modal ascriptions have reasons behind them: “A thing is called necessary either by reason of its essence or by reason of its cause” (Ip33s1). But we can raise a higher-order question: for what reason(s) do modal ascriptions work in the way that Spinoza claims they do? For ease, let us focus on modal properties instead of modal ascriptions. The question is similar to the one raised earlier about causation. What explains causation itself? Arguably, Spinoza’s answer is that causal relations obtain in virtue of conceptual connections between causal relata. A parallel question can be raised about modality itself. Do basic modal properties obtain in virtue of other, non-modal properties or is modality primitive for Spinoza?