How general was Newton’s experimental philosophy?

Posted on October 4, 2016 by Kirsten Walsh

Kirsten Walsh writes…

Newton is often taken to have spawned two important, but different, sciences: an experimental science exemplified in the Opticks, and a mathematical science exemplified in the Principia.  I. Bernard Cohen and George Smith, for example, write:

There is, perhaps, no greater tribute to the genius of Isaac Newton than that he could thus engender two related but rather different traditions of doing science.

Like many commentators, they emphasise the differences between the austere, formal mathematism of Newton’s so-called ‘rational mechanics’ and the complex and sophisticated experimentalism of his work on light and colour.  And so, the two works are typically taken to exemplify very different methodologies.

In contrast, on this blog, I have emphasised the common features, rather than the differences—presenting a more integrated account of Newton’s methodology.  For example, I have argued that his claim, that the Principia is a work of experimental philosophy, is something we should take seriously.  And so the mathematico-experimental method is a feature of both the Opticks and the Principia.  Moreover, I have argued that Newton’s mathematico-experimental method can be broadly characterised by an epistemic triad: a three-way epistemic division between theories, hypotheses and queries.  The epistemic triad drives Newton’s optical work and his rational mechanics in a trajectory from experiment to certainty, using mathematical reasoning.

While the Opticks and the Principia represent two fields to which Newton made important contributions, these impressive tomes do not signify the entirety of his research output—nor even the bulk.  During his lifetime, Newton produced vast quantities of written work on chymistry, theology and Church history, as well as mathematics.  Over several posts, I plan to explore some of this less well-known work in order to learn more about Newton’s methodology.  In particular, I want to see what kinds of methodological continuity, if any, there are between his many projects.

This may seem like a fool’s errand.  Indeed, these lesser-known parts of Newton’s research have a poor reputation.  One idea, floated by Jean-Baptiste Biot in his 1829 biography, was that Newton’s intellectual life divided naturally in two: prior to his mental breakdown in 1692, Newton’s life was sane, rational and scientific, but afterwards was mad, irrational and religious.  And so Newton’s alchemical and theological manuscripts are often dismissed as the half-baked musings of an old man.  In more recent times, however, commentators such as Betty Jo Teeter Dobbs, William R. Newman, Rob Iliffe and Sarah Dry (to name just a few!) have aimed to redress this situation.  They have demonstrated that Newton’s alchemical and theological pursuits were as much a part of his intellectual life as the optics, rational mechanics and mathematics, for which he is famous.  So, firstly, if there was any kind of cleavage, it was not along disciplinary lines, and secondly, these intellectual pursuits should be counted as serious scholarship—not simply to be swept under the proverbial rug.

So what sorts of continuities should we expect to find?  In the remainder of this post, I’ll offer a few preliminary suggestions.

One striking feature of Newton’s published scientific work is how methodologically reflective it was.  Perhaps we should expect similar reflections in his manuscripts on chymistry, theology or Church history.  Indeed, a cursory look at the collection shows that Newton approached chymistry, theology and Church history with the same persistence and vigour that we find in his other work.  Moreover, we can recognise several of the same methodological and foundational concerns.  For example, Newton’s interest in the restoration of an ancient tradition of knowledge that has been lost or corrupted, and the view that reason, hard work and disciplined empirical research are always preferable to speculation.

Another feature of Newton’s work that I have discussed on this blog is what I call his ‘rhetorical style’: Newton borrowed familiar terms and bent them to his own needs.  He is, moreover, best characterised as a methodological omnivore—he read widely on different methodologies and approaches, and selected from among them the best tools for the job.  We might expect to find the same thing in his chymistry and theology.  Again, my preliminary reading offers some support.  Newton appears to have been interested in all aspects of chymistry—a heavily experimental discipline, often with a pragmatic eye to profit, as much about developing chemical technologies and pharmaceuticals as it is about turning base metals into gold.  However, while Newton worked on the typical alchemist’s project of deciphering ancient myths, he doesn’t seem to have drunk the Kool-Aid.  He appears to have been much more concerned with linking his chymical research to his more mainstream science—for example, his matter theory.  In short, in these manuscripts, we can recognise the same desire to penetrate appearances and arrive at the fundamental truths of nature that we find in his physics.

Following on from this, we might also expect to find a concern for unification: the idea that Newton’s many topics of investigation are in fact part of a larger project.  For example, in Query 31 of the Opticks, Newton argues for both ontological and methodological unification.  Again, looking briefly at some of his alchemical manuscripts, we see a similar preoccupation.  Newton’s discussions of the ‘vegetative spirit’, for example, offer insight into the ways in which the various strands of his scholarly endeavours, including chymistry and theology, were united under one grand scheme.

When understanding the development of Newton’s thought, I often find it helpful to distinguish between Public-Newton and Private-Newton.  I have argued that there are important methodological differences between the work that Newton published (and hence, was willing to assert and defend) and the work he kept private.  While the former conforms, in some sense, to the experimental philosophy, the latter is typically much more speculative.  The distinction is particularly useful when considering Newton’s optical work, where we find stark differences between draft material and the final published version.  But I suspect it won’t be so useful once we turn to his chymistry, theology and Church history, where many of Newton’s unpublished manuscripts were in circulation—some only among his closest circle of like-minded friends, and others, much more widely.  And yet, this raises one final issue.  Newton’s efforts to pass off his published work as experimental philosophy may well have been politically motivated: by describing his work as ‘experimental philosophy’, he was signalling his commitment as much to the Royal Society as to observation- and experiment-based theorising.  His chymical, theological and Church history manuscripts were circulated much more privately—and presumably the same political motivations did not apply.  When working outside the jurisdiction of the Royal Society, did Newton conform to the experimental philosophy?

I’d love to hear your thoughts on this!

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