 Despite the pragmatic character of this definition, Lavoisier felt free to speculate about the compound nature of the earths, as well as the formation of metal oxides which required the decomposition of oxygen gas. Thus, Lavoisier also developed the notion of an element as a theoretical, last point of analysis concept. While this last point of analysis conception remained an important notion for Lavoisier as it was for Aristotle, his notion was a significant advance over Aristotle’s and provided the basis for further theoretical advance in the 19th century (Hendry 2005).