Michael Della Rocca has provided an influential interpretation of Spinoza relying heavily on the principle of sufficient reason. In order to challenge this interpretation, I identify three assumptions Della Rocca makes about the PSR and demonstrate that it is not clear Spinoza shares them. First, Della Rocca contends that the PSR is unlimited in scope. I show that the scope of Spinoza’s version of the PSR is ambiguous. While it is clear that substances and modes are included, it is unclear just how widely the scope extends. Second, Della Rocca argues that the PSR demands there are no illegitimate bifurcations. I argue that Della Rocca’s account of illegitimate bifurcations is too strong. I show that Spinoza offers a distinction in explanatory types that should be considered illegitimate and inexplicable according to Della Rocca’s definition of illegitimate bifurcations. Third, Della Rocca argues that explanations which satisfy the demands of the PSR must be in terms of the concepts involved. I show that Spinoza does not use conceptual explanations. Instead, in almost all cases, the explanations Spinoza relies on to satisfy the demands of the PSR are in terms of a thing’s cause.