Abstract

This paper traces the principal thematic developments in Aristotle’s conception of chemical substance as they bear on the evolution of the notion into modern times. A line of speculation is indicated about the interpretation of elemental proportions clearly raised by Aristotle’s discussion but not pursued in his extant writings. Apart from its historical interest, Aristotle’s discussion of substance and mixture has been taken up in contemporary systematic philosophy (Fine 1995), where it is treated as at best only relevant to ordinary, everyday views. This approach gains support from the contention that such views have been superseded by the molecular conception of chemical substance developed in 19th century science and extolled by advocates of the Kripke-Putnam conception of microessentialism (Kripke 1980, Putnam 1975). Duhem (1902), who well understood what would now be called the macroscopic theory of thermodynamics and its relevance to chemistry, had a different view, and the present discussion is much influenced by him. Certainly, Aristotle’s view stands in need of modification in the light of the understanding of mixtures provided by Gibbs’ phase rule (Gibbs 1948). But with a certain weakening, a central Aristotelian claim about mixtures still has some bearing.