A highly condensed account of the author's present view of some philosophical problems unresolved in The Structure of Scientific Revolutions. The concept of incommensurability, now considerably developed, remains at center stage, but the evolutionary metaphor, introduced in the final pages of the book, now also plays a principal role.

Mi Gyung Kim (2008) has challenged the historiographical assumption that phlogiston was the paradigmatic concept in eighteenth century chemistry. Her analysis of the operational, theoretical, and philosophical identities of phlogiston demonstrates how Stahlian phlogiston was appropriated into the burgeoning field of affinity theory. However, this new French conception of phlogiston was destabilized by the introduction of Boerhaave's thermometrics. By extending this story through 1790, I will show that British pneumatic chemists integrated new understandings of heat with an affinity based operational (...) definition of phlogiston and thereby stabilized the concept. What resulted was a new and very different phlogiston. (shrink)