The question is whether Spinozism, on a strong enough reading, refutes itself. In particular, does it make sense to say that finite things exist necessarily? According to Spinoza, it is absurd to suppose that a finite mode always exists necessarily.
[T]he idea is that which basically constitutes the being of the human mind… [But it is not] the idea of an infinite thing, for an infinite thing must always necessarily exist, and this is absurd (2p11d).
On the other hand, all that is within God’s power necessarily exists (2p3d). The upshot of juxtaposing these propositions seems to be that, in the case of finite modes, necessary existence ≠ existence at all possible times. Now, I prefer to think of necessary existence as existence in every possible scenario – where any possible time is a possible scenario – but that characterisation does not follow from the bare idea of existence in every possible world. Which account of necessary existence is correct? In part this is a terminological question. To the extent it is substantive I have two observations to make. In favour of my (i.e. Williamson’s) understanding of necessary existence, it might be thought that necessary existence just is the impossibility of non-existence. But read straightforwardly that requires eternal existence, and not only the necessity of world-membership. However, it must be admitted that there is prima facie plausibility in denying that the PSR requires anything more than the latter.
In any case, the lack of adequation between necessary world-membership and necessary eternity is compatible with the following ambiguity: when Spinoza says that the essence of man does not involve necessary existence (2ax1), this can be taken as referring to both the formal and actual essence of man. The formal essence entails the possibility of the finite mode rather than its existence, but is itself an infinite mode that always exists necessarily (here I follow the excellent Don Garrett). By contrast, the actual essence is something like a quiddity, and is co-extensive with the existence of the finite mode: when it is given, the latter is given; and when the latter is taken away, so too is it taken away. This does not mean, however, that the actual essence, and hence the finite mode that I am, contingently exists. Rather I must exist when I exist, and if I die then I must die. Hence in the case of my actual essence, if not that of my formal essence, necessary existence ≠ existence at all possible times. The underlying idea here is that a sufficient reason r for the existence of x suffices for x at T1, T2, etc. Importantly, Spinoza needn’t accept that a proposition of the form ‘x exists’ has a truth value independently of its being indexed to a particular time or times.
- Don Garrett, ‘Spinoza on the Essence of the Human Body and the Part of the Mind That Is Eternal’, in Olli Koistinen ed., The Cambridge Companion to Spinoza’s Ethics, (CUP: 2009), pp. 284-302.
- Baruch Spinoza, Ethics, trans. Samuel Shirley, (Hackett: 1992).