In the course of developing his theory of what would now be called chemical substance, Aristotle introduces what appear to be two distinct definitions of element alongside his notion of mixt (homogeneous mixture). The present paper is concerned with the integration of these ideas in a uniform theory, which calls for some speculation about the import of elemental proportions in compounds.

The bulk of Duhem's writing which bears on the understanding of mixtures suggests he adopted an Aristotelian position which he opposed only to the atomic view. A third view from antiquity-that of the Stoics-seems not to be taken into account. But his lines of thought are not always as explicit as could be wished. The Stoic view is considered here from a perspective which Duhem might well have adopted. This provides a background against which his somewhat unorthodox Aristotelianism might be (...) understood. (shrink)