Recently, Michael Della Rocca argued not only that the PSR “provide[s] the key to unlocking many of the mysteries of Spinoza’s philosophical system” (2008: 9), but that Spinoza requires the reduction of the most basic philosophical concepts to reason or intelligibility. This alleged “double use of the PSR” stipulates (1) that everything must be explainable, and (2) that it should be (ultimately) explained in terms of intelligibility. Hence, according to Della Rocca, Spinoza reduces his major phi