This paper investigates the revolutionary conceptual changes that took place when the phlogiston theory of Stahl was replaced by the oxygen theory of Lavoisier. Using techniques drawn from artificial intelligence, it represents the crucial stages in Lavoisier's conceptual development from 1772 to 1789. It then sketches a computational theory of conceptual change to account for Lavoisier's discovery of the oxygen theory and for the replacement of the phlogiston theory.

This article addresses the historical problem of how it was possible for Lise Meitner and her nephew Otto Robert Frisch to arrive at their novel interpretation of nuclear fission at the end of 1938. To understand this requires an analysis of the origin and subsequent development of the liquid-drop model of the nucleus. We begin by discussing George Gamow’s conception of the liquid-drop model in 1928 and then explore its extension, particularly by Werner Heisenberg and Carl Friedrich von Weizsäcker, between (...) 1933 and 1936. We then examine the role played by the liquid-drop model in Niels Bohr’s theory of the compound nucleus between 1936 and 1938. We argue that these two stages in the development of the liquid-drop model focused on two distinctly different features of the model, its static and dynamic characteristics, which were employed to understand two distinctly different phenomena, nuclear mass defects and nuclear reactions and excitations. The liquid-drop model thus became embedded in two distinctly different scientific traditions. We conclude by showing how these two traditions merged in the minds of Meitner and Frisch, leading them to their interpretation of nuclear fission. (shrink)

There is substantial evidence that traditional instructional methods have not been successful in helping students to restructure their commonsense conceptions and learn the conceptual structures of scientific theories. This paper argues that the nature of the changes and the kinds of reasoning required in a major conceptual restructuring of a representation of a domain are fundamentally the same in the discovery and in the learning processes. Understanding conceptual change as it occurs in science and in learning science will require the (...) development of a common cognitive model of conceptual change. The historical construction of an inertial representation of motion is examined and the potential instructional implications of the case are explored. (shrink)

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.