The main thesis of Michael Della Rocca’s outstanding Spinoza book (Della Rocca 2008a) is that at the very center of Spinoza’s philosophy stands the Principle of Sufficient Reason (PSR): the stipulation that everything must be explainable or, in other words, the rejection of any brute facts. Della Rocca rightly ascribes to Spinoza a strong version of the PSR. It is not only that the actual existence and features of all things must be explicable, but even the inexistence – as well as the absence of any feature of any thing – demands an explanation. Della Rocca does not stop here, however. He feeds his PSR monster with some more powerful steroids and suggests that Spinoza advocates what he terms “the twofold use of the PSR.” It is not only that everything must be explained and made intelligible, but it must ultimately be explained in terms of explainability or intelligibility itself. This twofold use of the PSR is the key to the entire book. Della Roca’s strategy throughout the book is to argue that any key feature of Spinoza’s system – be it causality, inherence, essence, consciousness, existence, rejection of teleology, goodness or political right – must be explained, and ultimately it must be explained in terms of intelligibility. “Spinoza single-mindedly digs and digs until we find that the phenomenon in question is nothing but some form of intelligibility itself, of explicability itself” (Della Rocca 2008a: 2).
Della Rocca’s book came out together with a cluster of articles in which he develops in detail his new reading of Spinoza. In one of these articles, he warns the reader: “Don’t let me start” (Dell Rocca 2010: 1). The train that is about to embark leads to very bizarre terrain, and thus one should think twice before embarking on the “PSR Express.” In this paper I argue that the train was hijacked. This was a perfect crime: without anyone noticing it, the engine driver diverted the train to a new route, and as with other perfect crimes, it is none but the criminal himself who is capable of, and indeed will, bring about his own demise. As I will later argue, Della Rocca’s “PSR-on-steroids” will eventually cripple reason itself. But let us not run too fast, and start at the very beginning. I happily – or at least, so I think - board the “PSR Express.” I believe Spinoza is strongly committed to the PSR and makes very significant use of this principle, but, unlike Della Rocca, I do not think the PSR is the key to all mysteries Spinozist, nor do I believe Spinoza was committed to the reductionist program of explaining all things through intelligibility (i.e., the second use of the PSR).