A post on Newton's and Spinoza's metaphysics, Pt 3. Nature does nothing in Vain...with some Hume

I didn’t expect my post of 19th December to be my last digression of the year. So let me just state here that 2024 was unexpectedly blessed for me because during the Summer a change of meds removed my long covid symptoms. I have clearly been improving continuously since September. But despite the improvements and increasingly rich calendar, I have stuck to some life-style changes which (inter alia) include less screen time after 6pm. During the last academic week of the calendar year, I simply ran out of time for these digressions. So, I am sad I could not wish you, my loyal (and a few new) readers happy holidays and all that.

Anyway, happy 2025! Let’s celebrate the new year with this third in a series of digressions (recall; and here) on the fact that Newton and Spinoza appear to have strongly opposing views on the principle that Nature does nothing in vain. (I will present a version of this material at an invited session on formal causation at the Eastern APA in New York next week—say hi!) The second post was prompted by a fascinating note from an-up-and-coming Newton scholar, Areins Pelayo, who teaches at Grand Valley State University. She called me attention to Newton’s correspondence with the physician, William Briggs (1642 – 1704). Today’s digression is a follow up to that second one.

The third letter to Briggs (from 1685) is in Latin and was attached as a preface by Newton to the Latin Version of Briggs's (1685) Theory of Vision (made at Newton's request). So, unlike the earlier two letters to Briggs, this letter was publicly available to Newton’s contemporaries. Interestingly enough, when it was published Newton was knee-deep in drafting the first edition of the Principia (1686).

This preface to Briggs’ Theory of Vision includes the following principle, “Simplex etenim est Natura, & eodem operandi tenore in immense effectuum varietate sibi ipsa constare solet.” (p. 273—my page-references are to Edleston’s 1850 edition) That is, ‘for Nature is simple, and by the same principle of operation she is wont to maintain herself in an immense variety of effects.’ Now, this passage brings to mind the explanation of the first rule of reasoning: “For nature is simple and does not indulge in the luxury of superfluous causes.” (Cohen & Whitman translation, p. 794; Nature enim simplex est & rerum causis superfluis non luxuriat.”) In the first (1686) edition, this passage was called a ‘hypothesis.’ But Newton kept the wording of this principle in all three editions of Principia.

The simplicity of nature is embraced in the preface to Theory of Vision and Principia. In the preface to Brigg’s Theory of Vision, the principle that nature is simple is asserted to defend the legitimacy of using as a heuristic the positing of similar causes in different sensory modalities.

In fact, lurking in Newton’s preface to Briggs’s Theory of Vision is the further thought that the simplicity of nature is also a claim about the (hidden) identity of nature maintained over time despite that very same (apparent) nature giving rise to apparent dissimilar effects. That is, this preface helps explain Newton’s commitment to the idea that nature remains simple. Keep that in mind.

That is, the way I read the passage in the preface to Briggs’ Theory of Vision, is that there is a reason or explanation for this maintenance of self-identity over time despite giving rise to dissimilar effects. What this explanation is (other than it appeals to the very same tenor of operation), is actually not fully articulated. But whatever it is, is what the ancients used to call a ‘formal cause.’

In the rules of reasoning of Principia, the principle that nature is simple is first used to deny superfluous causes (and, thus, another articulation that nature does nothing in vain [recall the first two posts in the present series]). Newton then uses this principle that nature is simple in the explanation to rule 3 as a premise that “since nature is always simple” (emphasis added) in order to conclude, then, that we should avoid engaging ‘in idle fancies” which “ought not to be fabricated recklessly against the evidence of experiments.” P. 795)

So, here in the rules of reasoning, that nature is simple is also a claim that nature is in an important respect self-same or identical with itself. And so, this ontological principle is used to criticize (let’s call it) epistemological adventurism. Lurking here, is Newton’s more general critique of what is known as the method of hypotheses associated with mechanical philosophy. (In that philosophy, the explanatory gold-standard was an explanation in terms of the hypothesis that only the geometric qualities of colliding bits of matter are truly explanatory.)

That nature is always simple is actually question-begging in the first edition of the Principia. And Newton recognizes this by adding the fourth rule in the third edition (“In experimental philosophy, propositions gathered from phenomena by induction should be considered either exactly or very nearly true notwithstanding any contrary hypotheses, until yet other phenomena make such propositions either more exact or liable to exceptions.”) It’s not question begging or a brute fact, however, in light of the preface to Briggs’ Theory of Vision. Because it had already posited something like a formal cause as the explanation of this self-sameness of nature. Of course, what justifies that posit may not be so obvious. And it would have been another ground for the Leibnizian suspicion that in the mid 1680s, Newton flirts with a weird kind of Spinozism.

In the General Scholium, added to the second (1713) edition of Principia (and distancing Newton from the charge of Epicureanism and Spinozism), Newton replaces nature with God. And he appeals to the consensus among the philosophers to claim: “It is agreed that the supreme God necessarily exists, and by the same necessity he is always and everywhere,” (p. 942 emphasis added.) Here God’s necessity is the source, the ground, that is, the formal cause of non-trivial temporal (“always”) and spatial (everywhere) structure. (So this also removes the question begging nature of nature's selfsame identity). But crucially this necessity is not identified with God’s formal cause or hidden substance/nature (of which we are ignorant as Newton asserts in language adopted from Locke).

Now, I have explored how to think about this divine necessity as a source of temporal and spatial structure (in which God himself exists) elsewhere on Newton’s modal metaphysics. Here I just want to limit myself to the observation that neither in the preface to Briggs’ Theory of Vision nor in the rule of reasoning does Newton invite an inference toward the existence of final causes from the stipulation that nature is simple. So, in the mid-1680s, Newton’s embrace of an ordered nature appears to be without foundation. (As I noted in the second post of the series, that Newton accepts God’s beneficent ordering of nature is only evident to a very careful reader of Book 3 of Principia.) And it looks as if Newton would allow — in Spinozist fashion — for the existence of a formal cause or ground to nature’s self-same identity without requiring embrace of final causes. Of course, as Zvi Biener emphasized to me, this more Spinozist account of formal causation is much richer in ontological import than the Aristotelian and scholastic notion of formal causation.

However, in the general scholium, after denying that we know anything of God’s hidden substance, Newton does invite the inference to final causes from God’s ubiquity (and, especially, the “wisest and best construction of things” (p. 942)). That’s all I wanted to digress on today.

But let me close with an aside, when in his posthumously published Dialogues Concerning Natural Religion, Hume’s Philo explored the move from simplicity in natural philosophy to its role in justifying final causes in natural religion, he insinuates in Spinozist fashion that the assignation of final causes is itself a natural bias of our minds and that this natural cognitive bias is strengthened by our empirical experience in astronomy:

A purpose, an intention, a design strikes every where the most careless, the most stupid thinker; and no man can be so hardened in absurd systems, as at all times to reject it. That Nature does nothing in vain, is a maxim established in all the schools, merely from the contemplation of the works of Nature, without any religious purpose; and, from a firm conviction of its truth, an anatomist, who had observed a new organ or canal, would never be satisfied, till he had also discovered its use and intention. One great foundation of the Copernican system is the maxim, That Nature acts by the simplest methods, and chuses the most proper means to any end; and astronomers often, without thinking of it, lay this strong foundation of piety and religion. (12.2)[1]

In context Philo is criticizing the Cleanthes’ use of Newtonian natural philosophy as an edifice for Newtonian natural religion.

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[1] For discussion (but without focus on the Spinozism in the vicinity) see Schliesser, Eric. "Copernican revolutions revisited in Adam Smith by way of David Hume." Revista Empresa y Humanismo 13.1 (2010): 213-249, and Qu, Hsueh. "Hume on Theoretical Simplicity." Philosophers' Imprint 23 (2023). Neither author