Tradition and Innovation

Volume 56 of the series The University of Western Ontario Series in Philosophy of Science pp 52-102

Atoms and the ‘Analogy of Nature’: Newton’s Third Rule of Philosophizing

  • J. E. McGuireAffiliated withDepartment of History and Philosophy of Science, University of Pittsburgh

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As in the case of ancient atomism, the revival of atomistic doctrines in the seventeenth century gave rise to questions regarding the existence and properties of primordial entities. With their insistent emphasis on sensory experience as a foundation of physical knowledge, the English experimental empiricists were faced with various epistemological problems. The majority, such as Robert Hooke and Henry Power, believed that atoms could in principle be observed: hence their problem was not the nature of knowledge of the microscopic, but rather how our knowledge could be extended into that realm.1 Thinkess such as Henry More and Ralph Cudworth tended to the view that, even if we could observe atoms, it would not add to our knowledge of first principles.2 Newton, and to some extent Locke, were confronted with a more difficult problem. Simply stated it is this: are there justificatory principles by which to sanction inferences from what is observable to what in principle is unobservable? If the basis of natural knowledge is strictly confined to what is actually or possibly observable, how can any claims be established about the nature and existence of atoms? The following study will refer to these questions as the problem of transduction;3 moreover it will be concerned primarily to analyse Newton’s use of the phrase ‘the analogy of Nature’. In its best known context that phrase appears in the Rules of Philosophizing prefixed to the third Book of the Principia in 1713.