Peter Anstey writes …
The historiography of the Enlightenment over the last fifty years has focused heavily on the influence of the natural philosophy of Bacon and Newton and the philosophy of Locke on the French philosophes.
Surprisingly, however, the thought of Bacon, Locke and Newton has rarely been seen as part of the broader impact of the experimental philosophy movement: the focus has been on individuals and their thought and experimental philosophy has been regarded as an expression of the ‘empiricism’ of these thinkers. See for example, Jonathan Israel’s monumental Radical Enlightenment and Democratic Enlightenment, neither of which lists ‘experimental philosophy’ in its index and which tend to subordinate English experimental philosophy to empiricism. (The term gets a mere 4 entries in the index of his 983-page Enlightenment Contested.)
Now, one text that has been repeatedly cited as early evidence of the important impact of Newton is Buffon’s Translator’s Preface to his 1735 French translation of Stephen Hales’ Vegetable Staticks of 1727. But when we turn to the text itself it’s pretty clear that Newton is merely an exemplar of a broader phenomenon.
As we have argued many times on this blog, the experimental philosophy that emerged in England in the 1660s was characterized by an emphasis on observation and experiment, an aversion to theoretical systems and especially its decrying of hypotheses and principles. Let us look at Buffon’s Preface and see what he has to say about Hales’ book. He says:
- The novelty of the discoveries and the majority the ideas [of Hales’ book] will no doubt surprise natural philosophers. I know nothing better of its kind, and the genre itself is excellent, for it is only experiment and observation.
- … works founded on experiment, merit more than others. I can even say that in natural philosophy, one ought to search out experiments as much as one ought to be afraid of systems. I admit that there is nothing so good as to establish first a single principle, and then to explain the universe, and I am convinced that if one were so happy to divine it, all the pain that it takes to make experiments would be unnecessary. But sensible people see rather how much this idea is vain and chimerical: the system of nature probably depends upon several principles, principles that are unknown to us and their combination even less so.
- … It is by choice experiments, reasoned and followed, that one forces nature to reveal its secret. All the other methods have never succeeded.
- … Collections of experiments and observations are therefore the only books that can augment our understanding. Being a natural philosopher is not a matter of knowing what follows from this or that hypothesis, in supposing, for example, a subtle matter, vortices, an attractive force, etc. It is to know well that by which it comes and to understand that which is presented to our eyes. The understanding of effects will conduct us insensibly to that of their causes and will not trip us up into the absurdities that seem to characterize all systems.
- … It is this method that my author [Hales] has followed. It is that of the great Newton; that which Bacon, Galileo, Boyle, Stahl recommended and embraced; that which the Académie of Sciences has made it a law to adopt … (pp. iii–vi)
Notice the underlined words here: ‘experiment and observation’, ‘systems’, ‘vain and chimerical’, ‘hypothesis’. This passage bears all the hallmarks of an expression of the central doctrines of the experimental philosophy. This is reinforced by the gallery of greats that is listed: Bacon, Galileo, Boyle, Stahl.
The focus is not on individuals such as Newton at all, nor is it on empiricism. It is on the méthode of the experimental philosophy. This is what Voltaire had referred to just one year earlier in 1734 in his letter ‘On the Lord Bacon’ in his Letters concerning the English Nation, where he claimed that Bacon ‘is the Father of experimental philosophy’ and that ‘no one before the Lord Bacon was acquainted with experimental Philosophy’.
It is the experimental philosophy, and not Bacon or Newton, that Buffon is praising and advocating. The experimental philosophy, as discussed by Buffon, Voltaire, d’Alembert and Diderot, needs to become a central notion in our historiography of the Enlightenment.
Kirsten Walsh writes…
A while ago I argued that the queries in Newton’s early optical papers are not hypotheses. Rather, they are empirical questions that may be resolved by experiment. In Newton’s Opticks, however, his queries become increasingly speculative – especially the famous ‘Query 31’. What should we make of this? Did Newton abandon his early distinction between hypotheses and queries?
In his early optical papers, Newton explains that “the proper Method for inquiring after the properties of things is to deduce them from Experiments”. Having obtained a theory in this way, one should proceed as follows:
- specify queries that suggest experiments that will test the theory; and
- carry out those experiments.
He tells us that hypotheses have a role in this procedure. They may be useful for: (a) suggesting further experiments, as the first step toward specifying queries; and (b) ‘illustrating’ the theory to assist understanding.
The queries in Newton’s Opticks have been much talked about, and often Newton has been accused of slipping hypotheses into his work under the guise of the more-respectable query. To examine this claim, I looked at the draft manuscripts* of Newton’s Opticks; in particular, “The fourth book concerning the nature of light & ye power of bodies to refract & reflect it” (Add. 3970, 337-8).
The draft begins, as many of the other books of Opticks begin, with a list of observations, followed by numbered propositions. However, it contains little in the way of argument and virtually no discussion of experimental evidence. Shapiro points out that this is because this is a draft of an outline or plan of a book; not a draft of the book itself. The propositions are things that Newton hoped to prove. For example:
- Prop. 1. The refracting power of bodies in vacuo is proportional to their specific gravities.
Prop. 2. The refracting power of two contiguous bodies is the difference of their refracting powers in vacuo.
The draft contains a section entitled ‘The conclusion’, which contains five ‘hypotheses’. I am interested in ‘Hypothesis 2’:
- As all the great motions in the world depend upon a certain kind of force (wch in this earth we call gravity) whereby great bodies attract one another at great distances: so all the little motions in ye world depend upon certain kinds of forces whereby minute bodies attract or dispell one another at little distances.
- How the great bodies of ye earth Sun moon & Planets gravitate towards one another what are ye laws of & quantities of their gravitating forces at all distance from them & how all ye motions of those bodies are regulated by those their gravities I shewed in my Mathematical Principles of Philosophy to the satisfaction of my readers: And if Nature be most simple & fully consonant to her self she observes the same method in regulating the motions of smaller bodies wch she doth in regulating those of the greater… The truth of this Hypothesis I assert not because I cannot prove it. But I think it very probable because a great part of the phaenomena of nature do easily flow from it wch seem otherways inexplicable…
I. Bernard Cohen describes this as “a ‘whale’ of an hypothesis” – and he’s right! When Newton started writing out this statement, he intended for it to be ‘Proposition 18’. But at some point, he has scratched out ‘Prop 18’, and re-branded it as ‘Hypoth 2’. There is no real semantic difference between a proposition and a hypothesis, but, for Newton, there is an epistemic difference. Propositions are things that he is able to assert as true. Hypotheses are things that he is unable to assert, because he does not have the evidence. Newton clearly hoped to assert Proposition 18. But as he started to explicate it, he must have realised that he couldn’t prove it. Thus, he re-labelled it as a hypothesis.
When Newton abandoned the fourth book, and restructured the rest of his Opticks, this ‘Hypothesis 2’ appears to have been re-worked to become ‘Query 31’ in Opticks, 2nd edition (1717):
- Have not the small Particles of Bodies certain Powers, Virtues, or Forces, by which they act at a distance, not only upon the Rays of Light for reflecting, refracting, and inflecting them, but also upon one another for producing a great Part of the Phaenomena of Nature? For it’s well known, that Bodies act one upon another by the Attractions of Gravity, Magnetism, and Electricity; and these Instances shew the Tenor and Course of Nature, and make it not improbable but that there may be more attractive Powers than these. For Nature is very consonant and conformable to her self…
Here, there is an obvious semantic shift between hypothesis and query: the query is stated as a question. Some scholars have argued that this is the only difference between hypotheses and queries: in the Opticks, queries are simply Newton’s way of getting around his self-imposed ban on hypotheses. I claim that there is more to the shift than this. Newton is using the semantic structure of the query to explore a possible future research program. The epistemic difference between the query and the hypothesis is similar to the epistemic difference between Popper’s falsifiable and unfalsifiable theories. The former is testable-in-principle, whereas the latter is not; and testability is a necessary condition of something becoming well-tested.
There is a difference between Newton’s early queries and his later queries: the former are part of the process of justification; but the latter are part of the process of discovery. In a previous post I noted that:
- While Newton’s [early] method of queries is experimental, it does not appear to be strictly Baconian. For the Baconian-experimental philosopher, queries serve “to provoke and stimulate further inquiry”. Thus, for the Baconian-experimental philosopher, queries are part of the process of discovery. However, for Newton, queries serve to test the theory and to answer criticisms. Thus, they are part of the process of justification.
The queries in Newton’s later work seem closer to the Baconian tradition that inspired him.
That the themes of Hypothesis 2 and Query 31 appear in Rule 3 of Principia, raises questions about the status of Newton’s ‘Rules of Philosophising’ and how we should interpret the re-branding of ‘hypotheses’ as ‘rules’ in later editions of Principia. I’d love to hear what you think!
* Recently, Cambridge University put Newton’s papers online, making it possible for those of us who live ‘down under’ to examine copies of many of Newton’s manuscripts!
This is the second part of Steffen Ducheyne’s presentation of his new book, “The main Business of Natural Philosophy:” Isaac Newton’s Natural-Philosophical Methodology. You can find the first part here.
Steffen Ducheyne writes …
In the Principia (1687), Newton developed a detailed picture of how one may deduce causes from phenomena (for the technical details I refer to Chapters 2 and 3). Newton’s expression ‘deductions from phenomena’ has oftentimes been considered as a rhetorical tool by which he sought to distance himself from his opponents. However, close scrutiny shows, I believe, that Newton’s ‘deductions from phenomena’ have profound methodological significance as well. I do not, however, endorse the view that Newton’s Principia-style methodology was therefore non-hypothetical. Rather, what makes it methodologically interesting is that it encompassed procedures to minimize speculation and inductive risk in the process of theory formation. What is distinctive of Newton’s Principia-style methodology is that he established bi-conditional dependencies between causes and their effects from the laws of motion. In other words, the causes which Newton would later infer in Book III were backed-up and constrained by the laws of motion. Given these dependencies, Newton was able to present his derivations of the centripetal forces acting in our solar system as deductions and, hence, as ‘deductions from phenomena’. I want to emphasize, however, that Newton’s proceeding from phenomena to theory, i.e. his presenting of certain inferences as deductions from phenomena, taken as such is not what makes his method essentially different from hypothetico-deductivism. Rather, proceeding from phenomena to theory is the by-product of what genuinely makes Newton’s method distinctive from hypothetico-deductivism: the establishment of systematic dependencies backed-up by the laws of motion. These systematic dependencies, in other words, mediate between experimental or astronomical results and the very causes which account for these phenomena.
Once he had finished the Principia, Newton returned to his optical studies, which would eventually lead to the publication of the Opticks in 1704. Could he now methodize optics according to the highly sophisticated standards which he had developed in the Principia? In my view, the answer is negative. For instance, I have argued that Newton’s argument for the heterogeneity of light rests on an argument of uniformity that cannot be licensed by Newton’s second rule of philosophizing. I have also paid considerable attention to the problem of transduction which Newton encountered in his optical studies. In mechanics, the affected entities, i.e. the explananda – bodies moving along specific trajectories, and their constituent elements, namely, the particles constituting these very bodies – all have a theoretically salient property in common, namely, mass. Because gravity is proportional to mass and because the latter is additive, gravity is likewise additive. This allowed Newton to show that a body’s overall force can be decomposed into the individual forces of each of the bodies constituting that body and vice versa. In optics, by contrast, we do not know – at least not without speculating on the matter – the constituting elements of the explananda. In the Opticks Newton could not establish ‘deductions from phenomena’ because, in contrast to the physico-mechanical theory of the Principia, a mixed science describes a given phenomenon mathematically without an accompanying explanatory story. In other words, in the Opticks the inference of causes could not be constrained by a set of laws which carry information about the proximate causes involved.
By way of outro and also as a teaser, I would like to conclude by devoting some words to the provisionalism that characterized Newton’s later methodological thought. Newton’s provisionalism pervades the third and especially the fourth regula philosophandi, which were added in the second (1713) and third (1726) edition of the Principia, respectively. The provisionalism which Newton envisioned did not apply to the ‘deductions from phenomena’, but rather to propositions ‘rendered general by induction’ – at least evidence from Newton’s manuscripts leads me to believe so. Based on a careful study of Newton’s manuscripts, I have also succeeded in clarifying what Newton understood by qualities which cannot be “intended and remitted” and, on the basis of this, I have concluded that the Cohen-Whitman translation of “intendi et remitti” as “increased and diminished” is incorrect. I could say much more about my book, but I hope that this will suffice to get you interested in reading it.
Steffen Ducheyne writes …
The research team at Otago has kindly invited me to discuss some of the central ideas of my recent monograph “The main Business of Natural Philosophy”: Isaac Newton’s Natural-Philosophical Methodology. My aim in this and next week’s guest post is not to give a complete overview of my book, but rather to bring some salient features of Newton’s methodology to the fore insofar as they are relevant for the speculative-experimental distinction.
Newton sought to separate hypotheses from demonstrations from within natural or experimental philosophy. This, in my view, adds an interesting dimension to the speculative-experimental distinction, for it shows how the distinction was transformed and introduced in the realm of natural philosophy. Newton’s preoccupation with methodological rigour and his distaste of hypotheses led him to explicate the conditions under which our conclusions about the physical world are to be considered as truthful. In this process, he would develop a highly sophisticated methodological position the kind of which had never been seen before.
Before turning to a discussion of Newton’s methodology proper, however, I would like to say something on how I have approached Newton’s methodology. Oftentimes, Newton’s methodology has been approached as if it was a stable given that remained fixed throughout his natural-philosophical career. In my book I have argued that Newton’s methodological views developed alongside with his natural-philosophical research. In Chapter 5, moreover, I distinguish between four distinct phases in the development of Newton’s methodological thought. Furthermore, although Newton clearly favoured his Principia-style methodology, which sets out to physico-mathematically ‘deduce’ causes from their effects, and considered it as the one to be followed ideally, Newton also relied on different methodologies. For instance, in the demonstrative parts of the Opticks he made use of a mixed mathematics treatment and in its speculative parts he proposed hypotheses to be investigated further. In my monograph I have called attention to important diachronic and synchronic differences in Newton’s methodological thought.
Newton’s first optical paper (1671/2) was not only a scientific debut, he also introduced a new methodological ideal on how knowledge about the empirical world is to be established. That ideal consisted in deducing causes from phenomena with demonstrative certainty. In the unedited version of his first optical paper, Newton stated the following on his theory of the heterogeneity of white light: “For what I shall tell concerning them [i.e. colours] is not a Hypothesis but most rigid consequence, not conjectured by barely inferring ’tis thus because not otherwise or because it satisfies all phænomena […] but evinced by ye mediation of experiments concluding directly & without any suspicion of doubt.” In the same period, he criticized the use of hypotheses in natural philosophy. At this point, important features of Newton’s methodological views were in place: his rejection of hypotheses, his ideal of deducing causes from phenomena, his conviction that by injecting mathematics into natural philosophy the latter could partake in the certainty of the former, his endeavour to draw conclusions from experiments, and his desire to treat of light ‘abstractly’, i.e. without making statements on the nature of light. Yet, as I argue in detail in Chapter 4, Newton’s methodological position was at that point still lacking elaboration and justification. That Newton did not provide much detail on how the heterogeneity of white light is derived from the experimentum crucis illustrates the lack of elaboration that characterized Newton’s early methodological views. In next week’s post I will summarize just how Newton’s methodological views developed from the publication of the first edition of the Principia in 1687.