monism and the psr

Rebecca Goldstein gives us a particularly nice, brief portrait of Spinoza’s basic cast of mind, one dominated by the centrality of the principle of sufficient reason (PSR) to his philosophical system and its isotropic zest for unification.

On Goldstein’s reading, Spinoza allows only one logically possible world (meaning there could not have been nothing), and only one substance – though there are many things. Regarding this distinction, in general it is common to read Spinoza’s monism as being less than complete, less than maximally extreme or pure. Specifically, it is common to read him as denying existence monism, the view that only one thing exists.

What is interesting about Goldstein’s particular interpretation is that she combines a weak reading of monism – which denies existence monism – with a very strong reading of the collapse of logic and ontology, and of the PSR.


The implication of this reading is that these two things – strength of monism and strength of explanatory completeness – are distinct. Yet perhaps this is mistaken? This is a possibility I want to come back to in future posts, since it fascinates me to consider whether taking the PSR seriously requires, with a single gesture, the denials of ontological plurality and of contingency.

In relation to this point, it is interesting that Goldstein holds that it is the same intuition behind the conflation of logic and ontology and behind substance monism. This intuition – which she calls the fundamental intuition – is nothing other than the PSR. Because Goldstein herself draws the link between “logicism” of this sort and substance monism, and does so in terms of the PSR, I do not feel uncomfortable in imagining extensions or variants of her claim, which go beyond her reading of Spinoza’s monism and towards a stronger one. This is the possibility that intrigues me: from the PSR we get not only logicism but something like existence monism. This permits, in turn, a more damning modus tollens.

The PSR expresses a fundamental demand for explanatory completeness which, Goldstein tells us, is accepted by the rationalist without proof. The idea is to assume reason and see how far we can get – hence the PSR becomes a presupposition of reason. Goldstein holds that, for Spinoza, the PSR is just as much a presupposition of reason as the principle of non-contradiction (PNC). We can gloss “presupposition of reason” as “something you have to accept when you accept reason, on pain of self-refutation”. The supposition of a brute fact, to this way of thinking, is just as preposterous as the supposition of a true contradiction. Indeed the former may entail the latter: Goldstein’s Spinoza defends the view that the LNC entails the PSR, contrary to the (to me) more tantalising possibility that explanatory completeness is impossible, i.e. that a surfeit of explanations is a plenitude of truth. In any case, it seems that, to the extent that the PSR cannot itself be proven, the demand for explanatory completeness is one that, for finite cognisers at least, is destined to remain unfulfilled. In this way it is as if rationalism fashions for itself a necessary fidelity, one that ends by embracing in the infinite what it abhors in the finite: circular explanation.*

*(Circular explanation is necessary given that it is not enough just to say that the world is necessary, if this necessity is itself brute; and given that necessity cannot be explained by contingency.)


  • Rebecca Newberger Goldstein, ‘Explanatory Completeness and Spinoza’s Monism’, in Philip Goff ed., Spinoza on Monism, (Palgrave Macmillan: 2012), pp. 281-92.
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