 The notion of simplicity implicit here is introduced late in DG where in book II Aristotle claims that “All the compound bodies … are composed of all the simple bodies” (334b31). But if all simple bodies (elements) are present in all compounds, how are the various compounds distinguished? With an eye to more recent chemistry, it is natural to think that the differing degrees of the primary qualities of warmth and humidity that characterize different substances arise from mixing different proportions of the elements. Perhaps Aristotle makes a fleeting reference to this idea when he expresses the uniformity of a product of mixing by saying that “the part exhibit[s] the same ratio between its constituents as the whole” (DG I.10, 328a8–9 and again at DG II.7, 334b15).