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Author Archives: Kirsten Walsh

CFP: ‘Feeding on the nectar of the gods’: Appropriations of Isaac Newton’s thought, ca. 1700-1750

CFP: ‘Feeding on the nectar of the gods’: Appropriations of Isaac Newton’s thought, ca. 1700-1750

Centre for Logic and Philosophy of Science Vrije Universiteit Brussel, 5-6 July 2016

University Foundation
Egmontstraat 11 Rue d’Egmont
B-1000 Brussels, Belgium

The conference theme is the diffusion of Newton’s thought during the first half of the eighteenth century across Europe. The seeming ease with which Newton’s ideas were diffused has long been described as self-evident. State-of-the-art research has, however, shown that the spread and success of Newton’s corpus was far from obvious. More particularly, it has been suggested that the successful diffusion of Newton’s ideas was not merely determined by the obvious merits of the scientific claims which Newton developed in his two major works, the Principia (first edition: 1687) and the Opticks (first edition: 1704), but also by local factors and contexts, such as inter alia: (a) already established scholarly and educationally dominant traditions or systems; (b) theological and religious fractions, sensibilities, and worldviews; and (c) metaphysical and methodological orientations. Seen from this perspective, if we want to fully understand the successful spread of Newton’s ideas, we need to take into account the multifarious ways in which his ideas were appropriated in order to meet local ‘needs’. At the same time, we need to pinpoint the characteristics of those very ideas in virtue of which they could be successfully ‘exported’ to different intellectual and scientific hubs across Europe. The scientific committee welcomes presentations that contribute to our understanding of the spread of Newton’s thought across Europe from approximately 1700 to 1750.

Abstracts of approximately 500 words should be sent to the conference chair Prof. Dr. Steffen Ducheyne by 24 April 2016. Decisions will be made shortly thereafter. There will be room for 12 contributed presentations (20-22 minutes for the actual presentation + 10-8 minutes for Q&A). Abstracts will be evaluated anonymously by the scientific committee according to the following criteria: 1. quality, 2. relevance to the conference theme, and 3. capacity to engender a diverse coverage of the diffusion of Newton’s thought.

Keynote Speakers
Marta Cavazza (Universita di Bologna)
Tamas Demeter (Hungarian Academy of Science)
Steffen Ducheyne (Vrije Universiteit Brussel)
Mordechai Feingold (Caltech)
Niccolo Guicciardini (Universita degli Studi di Bergamo)*
Rob Iliffe (University of Oxford)
Scott Mandelbrote (University of Cambridge)
Stephen D. Snobelen (University of King’s College)

* Lecture sponsored by Belgian Society for Logic and Philosophy of Science.

More information here.

Understanding Newton’s Principia as part of the Baconian Tradition

Kirsten Walsh writes…

Lately I have been examining Baconian interpretations of Newton’s Principia. First, I demonstrated that Newton’s Moon test resembles a Baconian crucial instance. And then, I demonstrated that Newton’s argument for universal gravitation resembles Bacon’s method of gradual induction. This drew our attention to some interesting features of Newton’s approach, bringing the Principia’s experimental aspects into sharper focus. But they also highlighted a worry: Newton’s methodology resembling Bacon’s isn’t enough to establish that Newton was influenced by Bacon. Bacon and Newton were gifted methodologists—they could have arrived independently at the same approach. One way to distinguish between convergence and influence is to see if there’s anything uniquely or distinctively Baconian in Newton’s use of crucial experiments and gradual induction. Another way would be if we could find some explicit references to Bacon in relation to these methodological tools. Alas, so far, my search in these areas has produced nothing.

In this post, I’ll consider an alternative way of understanding Baconianism in the Principia. I began this series by asking whether we should regard Newton’s methodology as an extension of the Baconian experimental method, or as something more unique. In answering, I have hunted for evidence that the Principia is Baconian insofar as Newton applied Baconian methodological tools in the Principia. But you might think that whether Newton was influenced by Bacon isn’t so relevant. Rather, what matters is how the Principia was received by Newton’s contemporaries. So in this post, I’ll examine Mary Domski’s argument that the Principia is part of the Baconian tradition because it was recognised, and responded to, as such by members of the Royal Society.

Domski begins by dispelling the idea that there was no place for mathematics in the Baconian experimental tradition. Historically, Bacon’s natural philosophical program, centred on observation, experiment and natural history, was taken as fundamentally incompatible with a mathematical approach to natural philosophy. And Bacon is often taken to be deeply distrustful of mathematics. Domski argues, however, that Bacon’s views on mathematics are both subtler and more positive. Indeed, although Bacon had misgivings about how mathematics could guide experimental practice, he gave it an important role in natural philosophy. In particular, mathematics can advance our knowledge of nature by revealing causal processes. However, he cautioned, it must be used appropriately. To avoid distorting the evidence gained via observation and experiment, one must first establish a solid foundation via natural history, and only then employ mathematical tools. In short, Bacon insisted that the mathematical treatment of nature must be grounded on, and informed by, the findings of natural history.

Domski’s second move is to argue that seventeenth-century Baconians such as Boyle, Sprat and Locke understood and accepted this mathematical aspect of Bacon’s methodology. Bacon’s influence in the seventeenth century was not limited to his method of natural history, and Baconian experimental philosophers didn’t dismiss speculative approaches outright. Rather, they emphasised that there was a proper order of investigation: metaphysical and mathematical speculation must be informed by observation and experiment. In other words, there is a place for speculative philosophy after the experimental stage has been completed.

Domski then examines the reception of Newton’s Principia by members of the Royal Society—focusing on Locke. For Locke, natural history was a necessary component of natural philosophy. And yet, Locke embraced the Principia as a successful application of mathematics to natural philosophy. Domski suggests that we read Locke’s Newton as a ‘speculative naturalist’ who employed mathematics in his search for natural causes. She writes:

[O]n Locke’s reading, Newton used a principle—the fundamental truth of universal gravitation—that was initially ‘drawn from matter’ and then, with evidence firmly in hand, he extended this principle to a wide store of phenomena. By staying mindful of the proper experimental and evidentiary roots of natural philosophy, Newton thus succeeded in producing the very sort of profit that Sprat and Boyle anticipated a proper ‘speculative’ method could generate (p. 165).

In short, Locke regarded Newton’s mathematical inference as the speculative step in the Baconian program. That is, building on a solid foundation of observation and experiment, Newton was employing mathematics to reveal forces and causes.

In summary, Domski makes a good case for viewing the mathematico-experimental method employed in the Principia as part of the seventeenth-century Baconian tradition. I have a few reservations with her argument. For one thing, ‘speculative naturalist’ is surely a term that neither Locke nor Newton would have been comfortable with. And for another thing, although Domski has provided reasons to view Newton’s mathematico-experimental method as related to, and a development of, the experimental philosophy of the Royal Society, I’m not convinced that this shows that they viewed the Principia as Baconian. That is to say, there’s a difference between being part of the experimental tradition founded by Bacon, and being Baconian. I’ll discuss these issues in my next post, and for now, I’ll conclude by discussing some important lessons that I think arise from Domski’s position.

Firstly, we can identify divergences between Newton and the Baconian experimental philosophers. And these could be surprising. It’s not, in itself, his use mathematics and generalisations that makes Newton different—Domski has shown that even the hard-out Baconians could get on board with these features of the Principia. The differences are subtler. For example, as I’ve discussed in a previous post, Boyle, Sprat and Locke advocated a two-stage approach to natural philosophy, in which construction of natural histories precedes theory construction. But Newton appeared to reject this two-stage approach. Indeed, in the Principia, we find that Newton commences theory-building before his knowledge of the facts was complete.

Secondly, the account highlights the fact that early modern experimental philosophy was a work in progress. There was much variation in its practice, and room for improvement and evolution. Moreover, its modification and development was, to a large extent, the result of technological innovation and the scientific success of works like the Principia. Indeed, it was arguably the ability to recognise and incorporate such achievements that allowed experimental philosophy to become increasingly dominant, sophisticated and successful in the eighteenth century.

Thirdly, the account suggests that, already in the late-seventeenth century, the ESD framework was being employed to guide, and also to distort, the interpretation and uptake of natural philosophy. By embracing the Principia as their own, the early modern experimental philosophers intervened on and shaped its reception, and hence, the kind of influence the Principia had. This raises an interesting point about influence.

As I have already noted, it is difficult to establish a direct line of influence stretching from Bacon to Newton. But, by focusing on how Bacon’s program for natural philosophy was developed by figures such as Boyle, Sprat and Locke, we can identify a connection between Bacon’s natural philosophical program and Newton’s mathematico-experimental methodology. That is, we can distinguish between influence in terms of actual causal connections—Newton having read Bacon, for instance—and influence insofar as some aspect of Newton’s work is taken to be related to Bacon’s by contemporary (or near-contemporary) thinkers. Indeed, Newton could have been utterly ignorant of Bacon’s actual views on method, but the Principia might nonetheless deserve to be placed alongside Bacon’s work in the development of experimental philosophy. Sometimes what others take you to have done is more important than what you have actually done!

Conference: Experimental Philosophy Through History

Experimental Philosophy Through History

A one-day conference at New York University on February 20, 2016

Contemporary work in experimental philosophy investigates the relationship between empirical methods and philosophical questions. However, there is a rich history of thinking through the general issues surrounding armchair and experimental approaches to philosophy; for instance, such projects can be found in 19th century philosophy, early modern philosophy, and classical Chinese philosophy.

To explore these topics and philosophical questions at the intersection of experimental philosophy and history of philosophy, we will host a one-day conference. The conference will be held at New York University on February 20th, from 10:00 AM to 6:15 PM. The conference features six presentations, each with a paired commentary. Further information can be found here.  Please direct any questions to:

Peter Anstey (The University of Sydney)
discussion by Stephen Darwall (Yale University)

Scott Edgar (Saint Mary’s University)
discussion by John Richardson (New York University)

Alex Klein (California State University)
discussion by Henry Cowles (Yale University)

Hagop Sarkissian (Baruch College, CUNY)
discussion by Stephen Angle (Wesleyan University)

Kathryn Tabb (Columbia University)
discussion by Don Garrett (New York University)

Alberto Vanzo (University of Warwick)
discussion by Alison McIntyre (Wellesley College)

CFP: An Interdisciplinary Master class on the Nature and Status of Principles in Western Thought

An Interdisciplinary Master class on the Nature and Status of Principles in Western Thought

15–18 March 2016

Eligibility: Graduate students and post-doctoral researchers
Maximum attendance:  15 (selected by application)
Organisers: Dr Dana Jalobeanu (Director, IRH-UB) and Prof Peter Anstey (Sydney University)
Invited speakers: Dr Vincenzo de Risi (Max Planck Institute, Berlin) and Dr Aza Goudriaan (Vrije Universiteit, Amsterdam)

The purpose of this interdisciplinary master class is to examine the nature and status of principles across a variety of disciplinary domains and a variety of historical periods. The concept of principles is almost ubiquitous in Western thought: it is used in philosophy, natural philosophy, ethics, art, mathematics, politics and theology. One only needs to cite some of the canonical works of early modern philosophy, natural philosophy or art to appreciate the centrality of the notion: for example, Descartes’ Principia philosophiae (1644), Newton’s Principia (1687) and Taylor’s New Principles of Linear Perspective (1719). Yet to date there are few if any systematic treatments of the subject. This master class will address the following questions in relation to classical, Hellenistic, Renaissance and early modern thought:

  • Which disciplines appealed to principles?
  • What sorts of principles did they deploy?
  • How does one get epistemic access to these principles?
  • And what roles did principles play in the period and discipline under scrutiny?
  • How does the use of principles vary across disciplines and across historical periods?
  • Is the principles concept stable or subject to change?
  • Is there a typology of principles?
  • What is the relation between principles, axioms, hypotheses and laws?

The master class will include lectures, reading groups and seminars, as well as more informal activities (tutorials, and discussions). The master class will be set within the interdisciplinary environment of the Institute of Research in the Humanities, University of Bucharest. It aims to bring together up to fifteen post-docs and postgraduate students from different fields and willing to spend four days working together within the premises of the Institute, and under the supervision of experts in the field. The master class will also benefit from logistical support of CELFIS (Center for the Logic, History and Philosophy of Science), Faculty of Philosophy. Each student attending the master class will have the opportunity to give a twenty-minute presentation on the final day. Student contributions are voluntary.

How to apply
In order to apply for the master class send a CV (maximum 2 pages) and a short letter of intention to Dr Mihnea Dobre ( by 30 January 2016. The final list of participants will be announced on the website of the institute by 5 February 2016.

There is no registration fee.


HOPOS 2016 Call for Submissions


June 22-25, 2016, Minneapolis, Minnesota, USA


Keynote Speakers

Karine Chemla (REHSEIS, CNRS, and Université Paris Diderot)
Thomas Uebel (University of Manchester)


The International Society for the History of Philosophy of Science will hold its eleventh international congress in Minneapolis, on June 22-25, 2016. The Society hereby requests proposals for papers and for symposia to be presented at the meeting. HOPOS is devoted to promoting research on the history of the philosophy of science. We construe this subject broadly, to include topics in the history of related disciplines and in all historical periods, studied through diverse methodologies. In order to encourage scholarly exchange across the temporal reach of HOPOS, the program committee especially encourages submissions that take up philosophical themes that cross time periods. If you have inquiries about the conference or about the submission process, please write to Maarten van Dyck: maarten.vandyck [at]


To submit a proposal for a paper or symposium, please visit the conference website:

Baconian Induction in the Principia

Kirsten Walsh writes…

Recently, I have been looking for clear cases of Baconianism in the Principia. In my last post, I offered Newton’s ‘moon test’ as an example of a Baconian crucial instance, ending with a concern about establishing influence between Bacon and Newton. Newton used his calculations of the accelerations of falling bodies to provide a crucial instance which allowed him to choose between two competing explanations. However, one might argue that this was simply a good approach to empirical support, and not uniquely Baconian. In this post, I’ll consider another possible Baconianism: Steffen Ducheyne’s argument that Newton’s argument for universal gravitation resembles Baconian induction.

Let’s begin with Baconian induction (this account is based on Ducheyne’s 2005 paper). Briefly, Bacon’s method of ampliative inference involved two broad stages. The first was a process of piecemeal generalisation. That is, in contrast to simple enumerative induction, shifting from the particular to the general in a single step, Bacon recommended moving from particulars to general conclusions via partial or mediate generalisations. Ducheyne refers to this process as ‘inductive gradualism’. The second stage was a process of testing and adjustment. That is, having reached a general conclusion, Bacon recommended deducing and testing its consequences, adjusting it accordingly.

Ducheyne argues that, in the Principia, Newton’s argument for universal gravitation proceeded according to Baconian induction. In the first stage, Newton’s argument proceeded step-by-step from the motion of the moon with respect to the Earth, the motions of the moons of Jupiter and Saturn with respect to Jupiter and Saturn, and the motions of the planets with respect to the Sun, to the forces producing those motions. He inferred that the planets and moons maintain their motions by an inverse square centripetal force, and concluded that this force is gravity—i.e. the force that causes an apple to fall to the ground. And, in a series of further steps (still part of the first stage), Newton established that, as the Sun exerts a gravitational pull on each of the planets, so the planets exert a gravitational pull on the Sun. Similarly, the moons exert a gravitational pull on their planets. And finally, the planets and moons exert a gravitational pull on each other. He concluded that every body attracts every other body with a force that is proportional to its mass and diminishes with the square of the distance between them: universal gravitation. Moving to the second stage, Newton took his most general conclusion—that gravity is universal—and examined its consequences. He demonstrated that the irregular motion of the Moon, the tides and the motion of comets can be deduced from his theory of universal gravitation.

Ducheyne notes that Newton didn’t attribute this method of inference to Bacon. Instead, he labelled the two stages ‘analysis’ and ‘synthesis’ respectively, and attributed them to the Ancients. However, Ducheyne argues that we should recognise this approach as Baconian in spirit and inspiration.

This strikes me as a plausible account, and it illuminates some interesting features of Newton’s approach. For one thing, it helps us to make sense of ‘Rule 4’:

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.

Newton’s claim that, in the absence of counter-instances, we should take propositions inferred via induction to be true seems naïve when interpreted in terms of simple enumerative induction. However, given Newton’s ‘inductive gradualism’, Rule 4 looks less epistemically reckless.

Moreover, commentators have often been tempted to interpret this rule as an expression of the hypothetico-deductive method, in which the epistemic status of Newton’s theory is sensitive to new evidence. Previously, I have argued that, when we consider how this rule is employed, we find that it’s not the epistemic status of the theory, but its scope, that should be updated. Ducheyne’s Baconian interpretation supports this position—and perhaps offers some precedent for it.

Ducheyne’s suggestion also encourages us to re-interpret other aspects of Newton’s argument for universal gravitation in a Baconian light. Consider, for example, the ‘phenomena’. Previously, I have noted that these are not simple observations but observed regularities, generalised by reference to theory. They provide the explananda for Newton’s theory. In Baconian terms, we might regard the phenomena as the results of a process of experientia literata—they represent the ‘experimental facts’ to be explained. This, I think, ought to be grist for Ducheyne’s mill.

Interpreting Newton’s argument for universal gravity in terms of Baconian induction brings the experimental aspects of the Principia into sharper focus. These aspects have often been overlooked for two broad reasons. The first is that the mathematical aspects of the Principia have distracted people from the empirical focus of book 3. I plan to examine this point in more detail in my next post. The second is that the Baconian method of natural history has largely been reduced to a caricature, which has made it difficult to recognise it when it’s being used. Dana Jalobeanu and others have challenged the idea that a completed Baconian natural history is basically a large storehouse of facts. Bacon’s Latin natural histories are complex reports containing, not only observations, but also descriptions of experiments, advice and observations on the method of experimentation, provisional explanations, questions, and epistemological discussions. We don’t find such detailed observation reports in the Principia, but we do find some of the features of Baconian natural histories.

So, Ducheyne’s interpretation of Newton’s argument for universal gravitation in terms of Bacon’s gradualist inductive method proves both fruitful and insightful. However, recall that, in my last post, I worried that the resemblance of Newton’s methodology to Bacon’s isn’t enough to establish that Newton was influenced by Bacon’s methodology. If Bacon was just describing a good, general, epistemic method, couldn’t Newton have simply come up with it himself? He was, after all, an exceptional scientist who gave careful thought to his own methodology. Is Ducheyne’s discussion sufficient to establish influence? What do you think?

CFP: Bucharest Colloquium in Early Modern Science

A colloquium at the Institute for Research in the Humanities, University of Bucharest & The Center for the Logic, History and Philosophy of Science, Faculty of Philosophy, University of Bucharest:


CFP: Bucharest Colloquium in Early Modern Science

6th-7th November 2015


Invited speakers:

Daniel Garber (Princeton University)
Paul Lodge (University of Oxford)
Arianna Borrelli (Technical University, Berlin)


We invite papers by established and young scholars (including doctoral students) on any aspects of early modern philosophy/early modern science. Abstracts no longer than 500 words, to be sent to Doina-Cristina Rusu ( ) by September 10. Authors will be notified by September 15.



Dana Jalobeanu ( and Doina-Cristina Rusu ( ).


More details:




Crucial Instances in the Principia

Kirsten Walsh writes…

In the General Scholium, which concluded later editions of Principia, Newton described the work as ‘experimental philosophy’:

In this experimental philosophy, propositions are deduced from phenomena and are made general by induction. The impenetrability, mobility, and impetus of bodies, and the laws of motion and the law of gravity have been found by this method.

On this blog, I have argued that we should take this statement at face value. In support, I have emphasised similarities between Newton’s work in optics and mechanics. For example, I have considered the kind of evidence provided in each work, arguing that both the Principia’s ‘phenomena’ and the Opticks’s ‘experiments’ are idealisations based on observation, and that they perform the same function: isolating explananda. I have also emphasised Newton’s preoccupation in the Principia with establishing his principles empirically. Finally, I have suggested that this concern with experimental philosophy, in combination with his use of mathematics, made Newton’s method unique.

In my last blog post, I wondered if we should regard Newton’s methodology as an extension of the Baconian experimental method, or as something more unique. I have written many blog posts discussing the Baconian aspects of Newton’s optical work (for example, here, here and here), but the Baconian aspects of the Principia are less well-established. I can identify at least three possible candidates for Baconianism in the Principia. The first, suggested by Daniel Schwartz in recent conversation, is that book 3 contains what might be interpreted as Baconian ‘crucial instances’. The second, discussed by Steffen Ducheyne, is that Newton’s argument for universal gravitation resembles Bacon’s method of induction. The third, discussed by Mary Domski, is that the mathematical method employed in the Principia should be viewed as part of the seventeenth-century Baconian tradition. In this post, I’ll focus on Schwartz’s suggestion—the possibility there is a crucial instance in book 3 of the Principia—I’ll address the rest in future posts.

To begin, what is a ‘crucial instance’? For Bacon, crucial instances (instantiae crucis) were a subset of ‘instances with special powers’ (ISPs). When constructing a Baconian natural history, ISPs were experiments, procedures, and instruments that were held to be particularly informative or illuminative of aspects of the inquiry. These served a variety of purposes. Some functioned as ‘core experiments’, introduced at the very beginning of a natural history, and serving as the basis for further experiments. Others played a role later in the process. This included experiments that were supposed to be especially representative of a certain class of experiments, tools and experimental procedures that provided interesting investigative shortcuts, and model examples that came close to providing theoretical generalisations.

Crucial instances are part of a subset of ISPs that were supposed to aid the intellect by “warning against false forms or causes”. When two possible explanations seemed equally good, then the crucial instance was employed to decide between them. To this end, it performed two functions: the negative function was to eliminate all possible explanations except the correct one; the positive function was to affirm the correct explanation.

According to Claudia Dumitru, Bacon’s crucial instances have a clear structure:

  1. Specify the explanandum;
  2. Consider the competing explanations (these are assumed to exhaust the possibilities);
  3. Derive a consequence from one explanation that is incompatible with the other explanation(s);
  4. Test that consequence.

Are there any arguments in the Principia that look like crucial instances? I think there’s at least one: Newton’s famous ‘Moon test’. Let’s have a look at it.

In proposition 4 book 3, Newton used his Moon test to establish that “The moon gravitates toward the earth and by the force of gravity is always drawn back from rectilinear motion and kept in its orbit”. Here, Newton argued that the inverse-square centripetal force, keeping the moon in orbit around the Earth, is the same force that, say, makes an apple fall to the ground, namely, gravity. I think we can tease out the features of a Baconian crucial instance from Newton’s reasoning here.

Firstly, there is an explanandum: what kind of force keeps the Moon in its orbit and prevents it from flying off into space? Secondly, two possible explanations are provided: the force is either (a) the same force that that acts on terrestrial objects, namely, gravity; or (b) a different force. Thirdly, we have a consequence of (a) that is incompatible with (b): if the moon were deprived of rectilinear motion, and allowed to fall towards Earth, it would begin falling at the rate of 15 1/12 Paris feet in the space of one minute, accelerating so that at the Earth’s surface it would fall 15 1/12 Paris feet in a second. Finally, we see a test of that consequence: the calculations based on the size and motion of the Moon, and its distance from the Earth. The results are taken to support (a) and refute (b).

I have three concluding remarks to make.

Firstly, interpreting the Moon test as a crucial instance involves ‘rational reconstruction’. In the text, Newton starts by calculating the rate at which the Moon would fall, and shows that this supports proposition 4. But I think my reading of this as a crucial instance is supported by Newton’s concluding remarks:

For if gravity were different from this force, then bodies making for the earth by both forces acting together would descend twice as fast, and in the space of one second would by falling describe 301/6 Paris feet, entirely contrary to experience.

Here, Newton described the Moon test as a crucial instance: he used an observation to choose between two competing explanations of the explanandum.

Secondly, when looking for crucial instances in the Principia, it might be tempting to start with the phenomena, listed at the beginning of book 3. Elsewhere, I have argued that these resemble Newton’s experiments in the Opticks, which function as instances with special powers. But the label ‘crucial instance’ describes the function, not the content, of an empirical claim. And so, to see if they provide crucial instances, we need to consider how the phenomena are used. In fact, I think they do provide crucial instances for Newton’s rejection of Cartesian vortex theory in favour of universal gravitation, found at the end of book 2. But again, this requires rational reconstruction.

Finally, there is the issue of historical influence. I have shown that Newton employed the Moon test to decide between two competing explanations, and that this argument resembles one of Bacon’s crucial instances. However, one might think that this was simply a good approach to empirical support, and that Newton was using his common-sense. So perhaps we shouldn’t take this to indicate (direct or indirect) influence. And so I have a question for our readers: was this style of reasoning uniquely Baconian?


Master-class: Isaac Newton’s Philosophical Projects

A master-class at the Institute for Research in the Humanities, University of Bucharest:


Isaac Newton’s Philosophical Projects

6th-11th October 2015


The purpose of this master-class is to discuss and to set in context some of Newton’s philosophical, scientific and theological projects. It aims to address a number of well-known (and difficult) questions in a new context, by setting them comparatively against the natural philosophical and theological background of early modern thought. By bringing together a group of experts on various aspects of Newton’s thought with experts on Descartes, Bacon and Leibniz, the master-class facilitates interdisciplinary and cross-disciplinary perspectives

The activities of the master-class will consist of lectures, reading groups and seminars, as well as more informal activities (tutorials, and discussions). The master-class will be set within the interdisciplinary environment of the Institute of Research in the Humanities, University of Bucharest. It aims to bring together 15 students (post-docs and graduate students) coming from different fields and willing to spend 5 days working together within the premises of the Institute, and under the supervision of leading experts.


Invited speakers:

Rob Illiffe (Sussex), Niccolo Guicciardini (Bergamo), Andrew Janiak (Duke University)



Dana Jalobeanu, Kirsten Walsh


To participate:

There is no participation cost, but there are limited places available.  In order to apply for the master-class send a CV and a letter of intention to Dana Jalobeanu ( by August 15, 2015. The final list of participants will be announced on the web-site of the institute by August 30, 2015. If you want to present a short paper in the master-class, please send an extended abstract (no longer than 800 words).


More details:





Huygens and Newton

Kirsten Walsh writes…

In a previous post, I noted that, unlike other members of the Royal Society, Newton saw a role for mathematical reasoning in experimental philosophy. In many ways, it was this mathematical approach that distinguished his methodology from the Baconian experimental philosophy, adopted by Boyle and Hooke.  Given this distinctive mathematical bent, one might be tempted to suggest that Newton’s approach has far more in common with that of mathematicians such as Huygens, than with experimental philosophers such as Boyle and Hooke. (Indeed, Eric Schliesser argues for this position here.) In today’s post, I’ll examine this claim. First I’ll look at Huygens’ and Newton’s mechanics, then I’ll broaden the scope to consider their optical work as well.

Let’s begin by comparing Huygens’ Horologium Oscillatorium (or, the Pendulum Clock) with Newton’s Principia. The Horologium and the Principia are generally regarded as two of the three most important seventeenth-century works on mechanics (the third being Galileo’s Two New Sciences). We know that Newton read, and very much approved of, Huygens’ Horologium well before he began work on his Principia. So it is an obvious source of inspiration and influence for Newton’s work. Moreover, there are important similarities between them. Most obviously, they share fundamental assumptions and content, including axioms regarding motion, analyses of pendulum motion and theories of curves. Furthermore, each work, to some extent, re-derives Galileo’s work on mechanics. But the similarity runs deeper. Firstly, both works display a marked preference for classical-geometrical inference strategies. For one thing, they both exploit the axiomatic structure of geometry as a model of logical rigour. And for another, they employ geometrical diagrams to demonstrate propositions. Secondly, both works draw on experiment (for example, pendulum experiments) to establish the explananda.

Another similarity between the two works is that both authors remain agnostic with regard to the mechanism or cause of gravity. Newton’s (in)famous phrase, Hypotheses non fingo, is a declaration of this. And in part II of the Horologium, Huygens’ second hypothesis begins, “By the action of gravity, whatever its sources…” (my emphasis). On the face of it, this is a feature that unites them. But, despite appearances, it is at this point that they come apart.

After its publication, Huygens criticised the Principia for appearing to support action at a distance. Huygens was committed to the mechanical philosophy and, as far as he was concerned, Newton’s account of gravity couldn’t be given a mechanical explanation. Newton was not swayed. The fact that his account seemed to support an unsavoury metaphysical commitment did not deter him from appreciating its empirical success. In the preface to book 3 of the Principia, Newton wrote that he was wary of its inclusion, since

“…those who have not sufficiently grasped the principles set down here will certainly not perceive the force of the conclusions, nor will they lay aside the preconceptions to which they have become accustomed over many years…” (my emphasis).

Huygens did exactly what Newton was afraid of: he allowed his mechanical preconceptions to prevent him from appreciating “the force of the conclusions”.*  As far as Newton was concerned, “it is enough that gravity really exists and acts according to the laws that we have set forth”. (And in the final paragraph of the Principia we see that Newton hoped to conceive of gravity as a spirit or vapour—he had not given up on the possibility of a local-action explanation. However, he wasn’t willing to sacrifice the rigour of his account in order to provide one.)

And so, one difference between Newton and Huygens lies in their commitment to mechanical philosophy. Where, for Huygens, the ability to give mechanical explanations—appealing to the shape, size, motion and texture of corporeal bodies—is a requirement of natural philosophy, Newton sees this as a needless restriction. Although Huygens’ commitment to the mechanical philosophy aligns him closely with Boyle and other early members of the Royal Society, the mechanical philosophy and the experimental philosophy were distinct. Arguably, Newton’s decoupling of experimental and mechanistic philosophy is one thing that sets him apart from both the early Royal Society and Huygens.

Another difference between Newton and Huygens is revealed when we broaden the scope to consider their optical work as well. Newton, following Isaac Barrow, thought that there was a place for mathematical reasoning in optics and natural philosophy more generally. In mathematics, one can reason deductively from axioms to propositions, without epistemic loss. So too, Newton thought, one can reason in natural philosophy. And so, by starting with experimentally established axioms (or laws), one could reason deductively to propositions, without epistemic loss. In this way, Newton conceived of a ‘science of optics’, grounded in experiment and observation, and inferred via mathematical reasoning. In contrast, Huygens thought that optics required a very different approach than mechanics. Where, in mechanics, it was possible to reason mathematically, without epistemic loss; Huygens thought that the hypothetico-deductive method was more appropriate for optics.

In brief, Newton took his theoretical claims in optics to be certain, as they were (1) mathematically derived from axioms, which were (2) established by careful experiment. Huygens, like the early Royal Society, held that certainty is out of our reach, so the best we can hope to achieve is a high degree of probability. Here we see one way in which Newton diverges from the Baconian experimental philosophy. He distanced himself from the probabilism of the Baconian experimental philosophers—and Huygens.

Here we have seen that there are indeed striking similarities between Huygens’ Horologium and Newton’s Principia. But, if we want to understand their methodological outlooks, we may learn more by considering the differences. The points of disagreement between Huygens and Newton allows us to identify two very different methodological approaches. Huygens was undoubtedly a strong influence on Newton. As were Descartes, Barrow and Hooke—not to mention his early reading of Aristotelian textbooks, his later interest in Pappus, and the many contemporary works of logic and natural philosophy! Despite these influences, or perhaps because of them, the methodology ultimately developed and exemplified by Newton was utterly original. In a nutshell, he saw mathematical deductive inference as compatible with the observations and experiments of Baconian natural history.  In combining these, he forged a new method of experimental philosophy, which eventually superseded Baconian experimental philosophy.

And so, what was Newton’s relationship with the mathematicians? Well, Newton actively engaged with their methodological approaches, and took a lot from them. Just as he did with the experimental philosophers of the early Royal Society.  How distinctive was Newton’s approach?  Mary Domski has argued that the methodology of the Principia should be viewed as a natural extension of the Baconian experimental philosophy – and that this was recognised by Locke.  In my next post, I’ll examine this idea and try to nail down just what was original about Newton’s methodology.


* Incidentally, here I offer a different reading of this passage to the one offered by Eric Schliesser. Where Schliesser argues that Newton was rejecting “a whole package of practices that are (implicitly) captured by the ESD”, I argue that Newton was rejecting the mechanical philosophy. (On the historiography of the mechanical philosophy, including some thoughts on the relationship between the experimental philosophy and the mechanical philosophy, see Peter Anstey’s recent essay review.  He has also posted on the topic here and here.)