A post on Newton's and Spinoza's metaphysics, Pt 2. Nature does nothing in Vain and Sufficient Reason
Yesterday (recall), I started a series of posts on the fact that Newton and Spinoza appear to have strongly opposing views on the principle that Nature does nothing in vain. My intention, nicely signaled in the last paragraph of that post, was to tell a story leading up to Spinoza. But after my post I received 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 see here for the informative Wikipedia entry).
In her mail Pelayo sent me the Correspondence of Sir Isaac Newton and Professor Cotes : including letters of other eminent men, now first published from the originals in the library of Trinity College, Cambridge; together with an appendix containing other unpublished letters and papers by Newton; with notes, synoptical view of the philosopher's life, and a variety of details illustrative of his history, edited by J. Edleston, and published in 1850 (you can find an online copy here).
The correspondence with Briggs is initiated by Newton in response to his reading of Briggs’ Theory of Vision. There are two letters in English of which the second is far more detailed. Both letters are about the bio-physics of vision, a topic that is also hinted at various places in his Opticks. (Newton’s account of color invites interest in this topic.)
The first letter (of 20 June 1682) cuts off just as it gets really interesting with Newton pleading,
But apparently the meeting never happened, or Newton had been reassured that no public controversy would follow from his thoughts. (See also the start of the second letter on p. 265.)
Before I get to that second letter of 12 September 1682, I do want to mention there is also a third more formulaic letter (from 1685) in Latin that was attached as a preface by Newton for, according to Eddleston, the “Latin Version of Briggs's Theory of Vision (made at Newton's request) Lond. 1685.” This text also has a tantalizing passage that connects to our theme, but about that some other time.
The second letter of 12 September takes up the question about why objects appearing to both eyes are seen as one (or as he puts it later in the letter, “how is it the two motional pictures in ye sensorium come together & become coincident.” (p. 269))As Newton notes, this need not occur: “Distort one eye & you will see ye coincident images of ye object divide from one another & one of them remove of ye object divide from one another & one of them remove from ye other upwards downwards or sideways to a greater or less distance according as ye distortion is; & when the eyes are let return to their natural posture the two images advance towards one another till they become coincident & by that coincidence appear but one.” (p. 267)
Now, Newton’s official position is, I think, one of agnosticism, “what if I know not?” (p. 269) He then runs through a number of proposals (including one he ascribes to Cartesians). At one point the question turns on whether the optical nerves of both eyes are joined. If I understand Newton correctly, he seems to assume Briggs denies this. He then writes the following (which is the reason why Pelayo called my attention to the passage):
In the quoted passage Newton appeals to the principle that nature does nothing in vain in order to rule out redundant structure in nature. Here ‘nature does nothing in vain’ is also a principle of economy. But it is not quite the same as the version we find in Newton’s first rule of reasoning (where it is used to rule out superfluous causes in one’s explanations).
I don’t mean to deny that in some respects Newton’s style of reasoning here anticipates, as described yesterday, what Newton articulates in the “first” and second rule of reasoning,” that is, what follows from what I called ‘the principle of economy:’ in particular, the second of reasoning involves a commitment to the idea “the csauses assigned to natural effects of the same kind must be, so far as possible, the same.” And the first example he offers in his illustration of the second rule is “the cause of respiration in man and beast.” That is, in bio-physical sciences, the same organs and functions can be put on par in different animals and humans. (Again, recall the way Harvey had exploited this.)
What is especially striking, of course, is that redundant structure is ruled out in a priori fashion. I would be curious to learn of ancient anticipations of this move. And the rationalist sensibility is on full display because Newton appeals to a version of sufficient reason in doing so. God here is an economizing creator who would not add needless structure.
I don’t want to overdo the significance of the passage. Newton had already told us we don’t know how vision is unified. So, the appeal to sufficient reason is a move in ruling out a hypothesis he does not like. I don’t know of any case where he appeals to it to argue for a view he endorses. (But that is also an invitation to look!)
As it happens, a scholar Newton very much admired, Christiaan Huygens, was tempted by a God does nothing in vain argument in an unpublished manuscript (ca 1689). Rather than ruling out structure, this goes from existing structure to beneficiaries/functionality of it: I have quoted and discussed the passage before (here):
But such diversity and beauty of things is available on the other planets like our Earthly realm, surely they wouldn't lack a spectator! As the elegance and artful workmanship of the animals, and the colors and scents of the flowers seem to be made available for human admiration and delight, will there not be beings on these planets who [could] enjoy so many and so pleasing spectacles? ["Quod si igitur similis quaedam rerum varietas ac pulchritudo in caeteris planetis atque in Terra hac nostra viget, nunquid spectatore carebunt! an non ut animalium elegantia et artificiosa fabrica, florum colores atque odores ad hominum admirationem aut voluptatem comparata videntur, ita et in istis existent aliqui qui tantis spectaculis tamque jucundis fruantur."--Christiaan Huygens (ca 1689).
As I have noted, Huygens seems he attributes to God (or Nature) a kind of (anti-anthropocentric) aesthetic maximization and conservation principle: no natural beauty is wasted and so when natural beauty occurs it requires spectators to enjoy it. So, because the night-skies on other planets are lovely there must be extraterrestrials to enjoy it. Huygens's God would not waste the opportunity to have sentient beings enjoy aesthetic pleasure. (The principle disappears in Huygens’ published Cosmotheoros.)
We know that in 1688 and 1689, Huygens was knee deep in the Principia. And I think there are reasons to suspect that the underlying principle is itself derived from Newton. In the first edition of Newton's Principia (1686), God is mentioned only once, deep into the technical details of Book 3: ''Therefore God placed the planet at different distances from the sun so that each one might, according to the degree of density, enjoy a greater or smaller amount of heat from the sun'' (Book 3, proposition 8, corollary 5; quoted from the Whitman/Cohen translation, p. 814). This claim was removed in subsequent editions of the Principia, and Newton moved his natural theology -- without this particular argument -- to the new conclusion of the Principia, his General Scholium.
At least one person discerned the significance of Newton's remark in Book 3 of the Principia. As Bernard Cohen argues, in his (1690) Discourse on Gravity, Huygens comments on proposition 8 that it showed what kind of gravity ''the inhabitants of Jupiter and Saturn would feel,'' (quoted from Cohen's long introduction to the translation of the Principia p. 219). We know that Huygens had empirical reasons to doubt Newton's argument for the inverse-square law as a universal quality of matter, but Huygens certainly accepted an inverse-square rule for celestial gravity that governed the planets.
Despite the fact that the argument was removed after the first edition of the Principia, Kant, who knew his Huygens, also saw Newton's point: ''Newton, who established the density of some planets by calculation, thought that the cause of this relationship set according to the distance was to be found in the appropriateness of God's choice and in the fundamental motives of His final purpose, since the planets closer to the sun must endure more solar heat and those further away are to manage with a lower level of heat,'' (UNH, Part 2, section 2, 284–85 (271))
Let’s return to Newton. In the General Scholium (added to the Principia in 1713), in proposing a variety of Design Arguments, Newton calls attention to the significance of that particular ''diversity of created things, each in its [proper] place and time.' And Newton emphasizes then that the beauty/elegance of our solar system is mimicked by countless other solar beautiful systems, too far apart to be of interest to us (see here for text). But if nature does nothing in vain, then, perhaps inspired by Huygens, Newton posited God's design entails aesthetic appreciation of countless elegant solar systems by spectatorial extraterrestrials--a lovely, pleasing thought.
Okay, now we’re in a good position to return to Spinoza (who really disliked such aesthetic arguments hinting at design and lampoons them in the Appendix to Ethics 1). To be continued.