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Newton and the ESD

Kirsten Walsh writes…

We rang in 2013 by reconsidering our set of 20 core theses on the emergence and fate of early modern experimental philosophy.  While our general theses regarding the distinction between experimental and speculative philosophy (ESD) were unchanged, I altered several of the specific claims about Newton’s methodology.  In this post, I’ll focus on thesis 5 and why I changed it.

In 2011, I claimed that:

5.    The ESD is operative in Newton’s early optical papers.

By ‘operative’, I mean that Newton appears to frame his methodology in terms of the ESD and aligns himself with the experimental philosophers of the Royal Society.  While Newton’s methodology differed from his contemporaries in important ways (for example, unlike his contemporaries, Newton emphasised quasi-mathematical reasoning), it nevertheless reflects some of the key ideas and preferences of the Royal Society.  Previously, I have discussed Newton’s early anti-hypothetical stance and Newton’s early use of queries as evidence of this his preference for the experimental philosophy of the Royal Society.

I now have enough evidence to broaden the scope of thesis 5.  The ESD is operative in all of Newton’s scientific work; not just his early work:

5.    The ESD is operative in Newton’s work, from his early work on optics in the 1670s to the final editions of Opticks and Principia published in the 1720s.

Let’s start with Newton’s Opticks.  This book is widely recognised as a work of experimental philosophy.  Newton’s experimental focus is made explicit by the opening sentence (which appears in every edition):

    “My Design in this Book is not to explain the Properties of Light by Hypotheses, but to propose and prove them by Reason and Experiments…”

Moreover, the presence of queries and the absence of hypotheses reflect the epistemic commitments of the experimental philosophy.

Commentators often notice that, in later editions of Opticks, Newton’s queries become increasingly speculative.  This suggests that, despite his use of ESD-jargon, Newton was not following the experimental philosophy after all.  In response to this kind of objection, I have argued that these later queries perform a role that is distinct to that of hypotheses, and that this role is consistent with Newton’s methodology.  Moreover, the general features of Newton’s methodology reflect his commitment to experimental philosophy in opposition to speculative philosophy.  In short, the ESD is operative in every edition of the Opticks.

Now consider Newton’s Principia.  This book is often seen as less a work of experimental philosophy and more a work of mathematics.  However, I have argued that the methodological passages in the first edition of Principia, though sparse, make it clear that experiment is an important theme of this work.  Moreover, in the ‘General Scholium’, which was introduced in the 2nd edition in 1713, Newton makes his commitment to the experimental philosophy explicit.

Commentators often notice that Newton’s use of hypotheses in Principia, and their changing roles between the three editions, suggest that his methodology changes over time.  However, I have argued that, in all three editions, Newton’s use of hypotheses is consistent with his experimental method.  Moreover, the late introduction of Rule 4 in 1726 demonstrates that this commitment to experimental philosophy, in opposition to speculative philosophy, is long-lasting.  In short, the ESD is operative in every edition of the Principia.

To summarise, the notions of experiment, queries and a decrying of speculative hypotheses that are enduring themes in Newton’s work, from the 1670s to his death in 1727, support my broader thesis 5.  Commentators often see Newton’s use of these notions as rhetorical and argue that he failed to follow his own methodology.  However, I argue that Newton’s methodology is internally consistent.  Moreover, these methodological statements are more than ‘mere’ rhetoric.  Rather, to some extent they track his epistemic and ontological commitments.

Do you think my argument is convincing?  I’d love to hear what you think about my conclusion.

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