John Locke and Natural Philosophy (review)

This book emerges from Peter Anstey’s collaboration with Lawrence Principe in editing Locke’s writings on natural philosophy and medicine for the Clarendon edition of Locke’s Works. It is both a commentary on those writings and an exploration of their relationship with Locke’s best-known work, An Essay concerning Human Understanding. In addition to Locke’s published works, Anstey draws extensively on Locke’s notes and his voluminous correspondence with other luminaries of the Scientific Revolution, most notably Boyle and Newton but also lesser known figures such as Sydenham, Stillingfleet, and Molyneux. Much of this material has not been previously examined and indeed the authorship of some surviving works, in particular Locke’s reviews of others’ works, remains undetermined.

In his introduction, Anstey explains that, in the seventeenth century, philosophy was commonly divided into moral and natural philosophy, the latter of which was further subdivided into experimental or speculative methodologies. Descartes was regarded as the foremost exponent of the speculative school which developed systems based on first principles. Bacon, followed by Boyle, championed the experimental school, which aimed to construct natural histories based on experiment and observation. Locke followed Bacon and Boyle but from the 1690s was also influenced by Newton, whose Principia introduced a mathematical approach, which ultimately became dominant. Locke himself was a physician, and medical concerns continued to influence his philosophical interests.

Anstey’s study seeks to establish four theses. Firstly, that Locke was committed to experimental natural philosophy and sceptical of the epistemic status of speculative systems. Secondly, that he believed a demonstrative science was unobtainable and hence the development of Baconian natural histories was the most effective method for the advancement of knowledge. Thirdly, that Locke, like Boyle and Hooke, practised speculative natural philosophy and that, like Boyle, he favoured the corpuscularian hypothesis (that matter consisted of small sub-microscopic particles) and mercurialist transmutational chymistry (derived from Paracelsus, Van Helmont, and the alchemical tradition as opposed to the Galenic theory of the humours). Finally, that Locke was influenced by the mathematical experimental method of Newton, which led him to change his views in the 1690s.

Chapter 1 examines Locke’s aims in writing the Essay concerning Human Understanding and concludes that his preference for the experimental over the speculative approach stemmed from pessimism about obtaining direct epistemic access to the real nature or essence of things. This view is further developed in the next chapter where the problem of corpuscular pessimism is seen to underlie Locke’s endorsement of the natural historical method, that is the accumulation of observations concerning a particular matter. Chapter 2 goes into greater detail about Locke’s debt to Bacon, his relationship with Boyle, and his own attempts at natural philosophy, ranging from experiments for Boyle on the pressure of gases in mines to attempts at epidemiology to test the miasma theory of disease.

Anstey next looks at Locke’s attitudes to hypotheses and analogy. He concludes they were considerably less favourable than is generally believed, and hence Locke should not be regarded as a precursor of modern scientific practice in this respect. Locke endorsed Newton’s demolition of Descartes’s vortex theory of planetary motion, grappled with competing theories on the biblical Deluge, and criticized Bernoulli’s theory of cohesion. Although Locke’s analytic skills were excellent, he was no mathematician. He was able to accommodate Newton’s mathematical method with his existing views on the status of mathematics and of demonstrative reasoning generally but realized that Newton’s use of foundational principles – principles that were actually justified by facts – challenged the natural history model of Baconian experimental philosophy.

Boyle had inspired Locke’s study of chymistry and Locke was one of three physicians to whom Boyle left his papers on the subject. Although Locke followed Boyle in his pursuit of the Sophic Mercury, he kept his distance from speculative theories and his interest in chymistry, as indeed his extensive botanical investigations (later used by Linnaeus), remained closely tied...