I agree [with Schliesser] that [I] Newtonian absolute time (p.18) should not be conflated with Newtonian true time. I agree that, for [II] the purposes of the Principia, Newton does not need his time parameter to extend from infinity to infinity. I agree that [III] the spatial reach of Newton’s time parameter in the Principia is an empirical matter. However, I do not think that, [IV] for Newton,“absolute” and “true” mark Schliesser’s distinction between a spatially limited empirical time parameter and a theologically motivated, infinitely extended “time.”
Initial doubts about Schliesser’s interpretation arise when we notice that in the scholium Newton does not make the positive assertion that absolute, true, or mathematical time are eternal in duration, nor does he assert that space is infinite, and nor does he assert that each moment of time extends from infinity to infinity. We are familiar with these claims from other places in Newton’s writings, but in this part of the text, where Newton is setting out what is needed for the project of the Principia, no such positive claims are made.
Moreover, the distinction that Schliesser draws is not one that we find doing work for Newton in his argument in the Principia, such that he has reason to mark it by means of a terminological distinction. As evidence for this, consider that Newton has just as good reasons to think that his absolute time extends to the physics of the distant stars and to the planetary systems around distant stars (if any such exist) as he does to think that his laws of motion and law of universal gravitation apply to such bodies, and he does not make the solar system the boundary of applicability for these latter.
Newton worried about how we extend our knowledge to bodies beyond the reach of our experiments, and this worry is explicitly addressed in his Rule 3 of Reasoning, added to Book 3 in the second edition of the Principia (Newton 1999, 795):Those qualities of bodies that cannot be intended and remitted and that belong to all bodies on which experiments can be made should be taken as qualities of all bodies universally.
This rule plays a crucial role in enabling Newton to extend results from terrestrial experiments to the celestial bodies of the solar system. In applying Rule 3 to bodies beyond the solar system, we would certainly be wise to be tentative given the flimsiness (even non-existence) of our empirical evidence, but there is nothing in Newton’s writings to indicate a sharp cutoff at the outer edges of the solar system such that we should not consider distant stars to be bodies. On the contrary, the possibility of other worlds around other Suns, governed by the same laws, is very much part of Newton’s thinking. For example, there is a manuscript in which Newton (p.19) asserts that the fixed stars are bodies just like our Sun: they are formed into spheres by their own gravity, and since they are bodies, they are, by definition, subject to the laws of motion. It seems to me that the distinction Schliesser draws is not important for Newton’s purposes.
Finally, the contexts in which Newton extends moments of time to spatial infinity are generally also those in which he is talking about God’s presence in the world, rather than those in which he is concerned with methods of reasoning from the phenomena.
In my opinion, we have good reason to suspect that Newton was careful not to overreach empirically when he was setting out his accounts of time and space in the scholium (i.e., at the outset of the empirical project of the Principia). There is therefore reason to doubt that the inclusion of “true time” is an “unnecessary addition” (Schliesser 2013, 91). In the following section I propose an alternative interpretation of the terminology, in which each of his three distinctions—absolute versus relative, true versus apparent, and mathematical versus common—are relevant and important for the project of the Principia.--Katherine Brading (2017) "Time for Empiricist Metaphysics" in Metaphysics and the Philosophy of Science: New Essays edited by Matthew Slater and Zanja Yudell [emphases added for ease of discussion.]
While it's pretty baffling to be told by a referee#2 to cite [fill in your name + year], there is, in academic life, no stranger feeling than to publish a scholarly paper about which one thinks firmly, 'this has to be wrong' and one simultaneously believes in exhilarated fashion, 'I am on to something really important.' So far I have only thought that once, when my Newton's Philosophy of Time (2013) appeared in print (thank you Adrian and Heather for seeing it through!)
Now, between (ca) 2007 and 2015, I was immersed in a collegial community of Newton scholars, which -- thanks to email and a steady stream of workshops -- shared papers and ideas regularly (Brading's letters were often at the root of my papers); and many of the best ideas in my Newton's Philosophy of Time paper originated with or had been commented on by them. And, in fact, the (2013) paper's core starting point, that we ought not assume that absolute and true time are identical, originates in reflecting on a paper by Nick Huggett, who had claimed that absolute and true motion should not be treated as the same concept in the famous scholium to the definitions of the Principia.
Somewhat strangely, while there is huge sophisticated literature on Newton's philosophy of space, there are only a few papers on Newton's philosophy of time. There is, however, a general presumption that Newton's treats them in more or less identical or at least symmetrical fashion as was more common in early modern world (Geoff Gorham has explored this). And Newton invites the idea when he writes, in the scholium to the definitions, 'Just as the order of the parts of time is unchangeable, so, too, is the order of the parts of space.'
In the scholium to the definitions, Newton tells us that space and time are both abstract "quantities" and that these can be distinguished "into absolute and relative, true and apparent, mathematical and common."
But alerted by Huggett's paper, I had noticed something quirky. Compare the following two sentences (they are both the first sentence of the respective paragraphs in which these quantities are explained):
[A]: Absolute, true, and mathematical time, in and of itself and of its own nature, without reference to anything external, flows uniformly and by another name is called duration.
[B] Absolute space, of its own nature without reference to anything external, always remains homogeneous and immovable.
'True, and mathematical' are absent in [B]! Now look at what Newton says about the relevant contrast (in the next sentence of each paragraph):
[A*] Relative, apparent, and common time is any sensible and external measure a (precise or imprecise) of duration by means of motion; such a measure—for example, an hour, a day, a month, a year—is commonly used instead of true time.
[B*] Relative space is any movable measure or dimension of this absolute space; such a measure or dimension is determined by our senses from the situation of the space with respect to bodies and is popularly used for immovable space, as in the case of space under the earth or in the air or in the heavens, where the dimension is determined from the situation of the space with respect to the earth.
Again, "apparent, and common" are absent in [B*].+ In addition, there is a further asymmetry in the measures. When the (regular) motion of bodies are used (qua measure of time), something physical is deployed to track an abstract quantity (viz. absolute time, etc.) But when the situation of one body relative to another body is used, it looks like the very abstraction you are trying to track is already in the measure. (Of course, this is also true of motion, qua measure, which presupposes the very abstract regularity you are trying to track.) But to put the point informally, Newton is proposing to treat a part of space as the measure of space. He treats something that is prima facie not time as the measure of time.+
This is not the place to recount what I did with these initial observations. You can infer some of what I claimed in my paper from some of Brading excellent criticisms quoted above. As I said above, I had strong feeling that something had gone wrong in my argument. And, as it happens, in the piece I partially quoted above, Brading has articulated the version of Newton's position that I would have expected to articulate myself (except that she does so much better than I could imagine myself doing) before I had started writing my own paper. And when I first heard her paper, and than read it when it appeared, I was both pleased she agreed with me on [I-III] and convinced she is right about the remaining differences between us, that is [IV].
But as she guessed in a recent note to me, I don't really believe in the inner recess of my heart that I am wrong about [IV]. And so here I want to begin spelling out why. And, rather than going to the heart of the matter, I start by sorting out some preliminary disagreements. Today I tackle two such disagreements. I fully agree with Brading that rule 3 "plays a crucial role in enabling Newton to extend results from terrestrial experiments to the celestial bodies of the solar system." And that, while there are epistemic risks, the rule also encourages to project "to bodies beyond the solar system." But notice that in the quote from Rule 3, Newton mentions bodies, or as David Miller has emphasized, systems or, as I (influenced by Chris Smeenk) would say, interactions among bodies in rule 3. He does not mention space or time in the rule.
And, in fact, in the Opticks, Newton had queried “it may be also allowed that God is able to create particles of matter of several sizes and figures, and in several proportions to space, and perhaps of different densities and forces, and thereby to vary the laws of nature, and make worlds of several sorts in several parts of the universe.” (Query 31; emphases added.) This passage is interesting for what Newton thinks about the nature of the laws of nature (see my (2017) piece with Zvi Biener, which engages with Brading's influential views on laws). But here I use it to note an important contrast: for Newton it is quite conceivable that bodies and the laws they obey could be different whereas he does not think space could be different. And, in fact, for Newton it is conceivable, as a speculative matter, that in solar systems (what he calls "worlds") far from ours bodies and their laws are different (such that the galaxy is populated (by "worlds of several sorts in several parts of the universe"). Such speculations are not to be used in active research (which is, in fact, governed by rule 3).
As an aside, because solar systems are so far apart, and separated by empty space, there is negligible interaction among them. (According to the general scholium, this is a providential thing because it prevents the solar systems from collapsing onto each other.) I say 'negligible' because light does reach us from afar. And there is no reason to think it obeys different laws.
But crucially, space cannot be created differently by God. And that is, as Newton explains in the general scholium,“by existing always and every where, [God] constitutes Duration and Space . . . ’Tis allowed by all that the supreme God exists necessarily; and by the same necessity he exists always and every where.” So, space, and time, are unchanging because they are constituted by God. In effect, they are privileged attributes of God. So, while time is not mentioned in the passage quoted from Query 31, it seems natural to read Newton as claiming that fundamentally time is necessarily unchangeable, while bodies could be different.
Okay, this puts me in position, to mark a second (less important) misconception (for which my terminology may be to blame). Brading appears to think that when I use 'rational theology' I mean unempirical. Now, it is true that I argue that unlike absolute time, true time is of no use in Newton's dynamics or the physics proper of the Principia. But by this I do not mean that true time is thereby unempirical. For, Newton is quite explicit in the general scholium that theology is, in part, an empirical enterprise: "to treat of God from phenomena is certainly a part of "natural" philosophy.""
But rather by 'rational theology' I meant (by way of analogue to 'rational mechanics') that there are features of Newton's theology that, while attentive to the phenomena, rely on conceptual moves and (what I have called (recall) Newton's 'modal metaphysics' [see also here; here]) from those phenomena and that (those moves) are not overdetermined by the empirical findings. So, for example, what grounds (true) time in God is a constitution relation governed by a species of necessity.
Now this second misconception is not just a terminological matter because for Brading Newton's contribution to metaphysics (and its history) is precisely to allow the kind of distinctions between true and absolute time to "become empirically tractable in the context of the project of the Principia (or some such project)." I think she is right about this, but that she also has a tendency to downplay the extra-empirical conceptual/metaphysical moves (e.g., constitution, necessity, etc.) Newton makes from the phenomena. (That is she turns Newton into an empiricist of a sort I don't think he is.) But I have gone on for too long today.
Notice that everything I have said thus far is compatible with Brading being right about how we should distinguish between true and absolute time in Newton and also that both kinds of time have a place in Newton's physics, that is, the project of the Principia proper. But to settle these matters it is not sufficient to nitpick about her criticism of my view, but I must engage with her "alternative view." [To be continued...]
+To be sure, if you read ancient philosophers you'll see that the motions of heavenly bodies are treated as measure of time or even time itself. So, I am not claiming that what Newton is doing would have been thought remarkable.
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