Meeting 41

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DATE: Tuesday, October 12

TIME: 1 PM Princeton time (ET) / 8 PM Bucharest time (UTC+2)

PANEL: Newton on Hypotheses

SPEAKERS: Areins Pelayo (University of Illinois) & Kirsten Walsh (University of Exeter)


The Metaphysical and Empirical Criteria in Newton’s Hypotheses

Areins Pelayo

Newton disdained ‘Cartesian hypotheses,’ yet admitted that hypotheses were useful if examinable  by experiments. Throughout his career, Newton tinkered with two theses: the corpuscularity of light and  the aether—two ideas that some commentators agree Newton treated as hypotheses. In this paper, I  propose six implicit criteria (four metaphysical and two empirical) that these two hypotheses satisfy,  which makes sense of Newton’s conflicting remarks on hypotheses. My proposal combines the partial  pictures of Cohen (1999, 1969), Dobbs (1991), Janiak (2008), Shapiro (1993), and Walsh (2014). The  four metaphysical criteria are (i) Non-contradiction, (ii) Parsimony, (iii) Mechanism, and (iv) Divine  Conformity. The two empirical criteria are (v) the Analogy of Nature and (vi) Experiment. I pay special  attention to how Newton’s theology and alchemy inform these criteria. For instance, because God could  not directly cause gravity, Newton speculated that an aether was its cause. I thus show, with these six  criteria, why it made sense for Newton to reject Cartesian hypotheses.

The Instrumental Roles of Newton’s Optical Hypotheses

Kirsten Walsh

Early modern experimental philosophers often appear to commit to, and utilise, corpuscular and mechanical hypotheses. This is somewhat mysterious: such hypotheses frequently appear to be simply assumed, odd for a research program which emphasises the careful experimental accumulation of facts. Isaac Newton was one such experimental philosopher, and his optical work is considered a clear example of the experimental method. Focusing on his optical investigations, I identify three roles for hypotheses. Firstly, Newton introduces a hypothesis to explicate his abstract theory. The purpose here is primarily to improve understanding or uptake of the theory. Secondly, he uses a hypothesis as a platform from which to generate some crucial experiments to decide between competing accounts. The purpose here is to suggest experiments in order to bring a dispute to empirical resolution. Thirdly, he uses a hypothesis to suggest an underlying physical cause, which he then operationalises and represents abstractly in his formal theory. The second and third roles are related in that they are both cases of scaffolding: hypotheses provide a temporary platform from which further experimental work and/or theorising can be carried out. In short, the entities and processes included in Newton’s optical hypothesis are not simply assumed hypothetical posits. Rather, they play instrumental roles in Newton’s experimental philosophy.

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