Locke and the Newtonian Achievement
Kirsten Walsh writes…
In the Principia, Newton claimed to be doing experimental philosophy. Over my last three posts, I’ve wondered whether we can interpret his so-called ‘experimental philosophy’ as Baconian. In the first two posts, I identified methodological similarities between Bacon and Newton: first, the use of crucial instances; second, the use of Baconian induction. In each case, I concluded that, without some sort of textual evidence clearly tying Newton’s method to Bacon’s, such similarities don’t demonstrate influence. In my third post, I tried a different approach: I considered Mary Domski’s claim that Newton’s Principia should be considered Baconian because members of the Royal Society recognised, and responded to, it as part of the Baconian tradition. While Domski’s argument was fruitful in helping us better to understand what’s at stake in discussions of influence, I raised several concerns with her narrative. In this post, I shall address those concerns in more detail.
Let’s focus on Domski’s account of how Locke reacted to Newton’s Principia. Domski argues that 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 short, Domski suggests that we read Locke’s Newton as a ‘speculative naturalist’ who employed mathematics in his search for natural causes. Last time, I expressed two concerns with this account. Firstly, ‘speculative naturalist’ looks like a contradiction in terms (I have discussed the concept of ‘speculative experimental science’ here), and surely neither Locke nor Newton would have been comfortable with the label. Secondly, there’s a difference between being part of the experimental tradition founded by Bacon, and being Baconian. Domski’s discussion of the reception of the Principia establishes the former, but not necessarily the latter.
We can get more traction on both of these concerns by considering Peter Anstey’s account of how the Principia influenced Locke. Anstey argues that Newton’s achievement forced Locke to revise his views on the role of principles in natural philosophy. In the Essay, Locke offers a theory of demonstration—the process by which one can reason from principles to certain truths via the agreement and disagreement of ideas. In the first edition, Locke argued that this method of reasoning was only possible in mathematics and moral philosophy, where one could reason from certain principles. Due to limitations of human intellect, such knowledge was not possible in natural philosophy. Instead, one needed to follow the Baconian method of natural history which provided, at best, probable truths. However, Anstey shows us that, by the late 1690s, Locke had revised his account of natural philosophy to admit demonstration from ‘principles that matter of fact justifie’ (that is, principles that were discovered by observation and experiment).
I now draw your attention to two features of this account. Firstly, Newton’s scientific achievement—his theory of universal gravitation—as opposed to his successful development of a new natural philosophical method per se forced Locke to revise his position on demonstration from principles. (A while ago, Currie and I noted that this situation is to be expected, if we take the ESD seriously.) This feature should make us suspicious of Domski’s claim that Newton’s Principia was taken to exemplify the speculative stage of Baconian natural philosophy. Locke did not see Newton’s achievement as a system of speculative hypotheses, but as genuinely empirical knowledge, demonstrated from principles that are justified by observation and experiment. Newton had not constructed a Baconian natural history, but nor had he constructed a speculative system. Rather, Locke recognised Newton’s achievement as something akin to a mathematical result—one which his epistemological story had better accommodate. This forced him to extend his theory of demonstration to natural philosophy. And so, by the late 1690s, we find passages like the following:
“in all sorts of reasoning, every single argument should be managed as a mathematical demonstration; the connection and dependence of ideas should be followed, till the mind is brought to the source on which it bottoms, and observes the coherence all along” (Of the Conduct of the Understanding).
Secondly, Anstey emphasises that Locke didn’t regard Newton’s mathematico-experimental method as Baconian, but only as consistent with his, Locke’s, theory of demonstration. (Anstey also claims that Locke never fully integrated the revisions required to his view of natural philosophy in the Essay.) On this blog, we have suggested that, in the 18th century, a more mathematical experimental natural philosophy displaced the natural historical approach. And Anstey has offered a sustained argument for this position here. He argues that the break was not clean cut, but in the end in Britain mathematical experimental philosophy trumped experimental natural history. That this break was not clean cut helps to explain why experimental moral philosophers, such as Turnbull, thought they were pursuing both a Baconian and a Newtonian project, and were quite comfortable with this.
Notice that I’ve shifted from the vexed question of the extent to which Bacon influenced Newton, to a perhaps more fruitful line of enquiry: how Newton influenced Locke and others. This is no non sequitur. The members of the Royal Society strove to understand Newton in their terms—namely, in terms of Baconianism and the experimental philosophy. Here, it seems that two conclusions confront us. Firstly, we (again) find that Newton was taken as legitimately developing experimental philosophy by emphasising both the role of experimentally-established principles of natural philosophy and the capacity of mathematics to carry those principles forward. These aspects are, at best, underemphasised in Bacon and certainly missing from the Baconian experimental philosophy adopted by many members of the Royal Society. Secondly, we see that Newton’s influence on Locke was due, at least in part, to his scientific achievements. Newton did not argue directly with Locke’s epistemology or method, nor did Locke take Newton’s methodology as a replacement for his own. Rather, Locke took Newton’s scientific success as an example of demonstration from ‘principles that matter of fact justifie’. This, in turn, necessitated modifications of his own account.
