science tend to emphasize the norms of modern science, internalist histories can also consider the different systems of thought underlying the development of Babylonian astronomy or Medieval impetus theory. In practice, the line between internalism and externalism can be incredibly fuzzy. Few historians then, or now, would insist that either of these approaches in their extremes paint a wholly complete picture, nor would it necessarily be possible to practice one fully over the other. However, at their heart they contain a basic question about the nature of science: what is the relationship between the producers and consumers of scientific knowledge? The answer to this question must, in some form, inform the method in which the history of science and technology is conducted; conversely, how the history of science and technology is conducted, and what it concludes, can inform the answer to the question. The question itself contains an entire host of philosophical questions: what is the nature of scientific truth? What does objectivity mean in a scientific context? How does change in scientific theories occur? The historian/sociologist of science Robert K. Merton produced many works following Hessen's thesis, which can be seen as reactions to and refinements of Hessen's argument. In his work on science, technology, and society in the 17th-century England, Merton sought to introduce an additional category — Puritanism — to explain the growth of science in this period. Merton split Hessen's category of economics into smaller subcategories of influence, including transportation, mining, and military technique. Merton also tried to develop empirical, quantitative approaches to showing the influence of external factors on science. Even with his emphasis on external factors, Merton differed from Hessen in his interpretation: Merton maintained that while researchers may be inspired and interested by problems which were suggested by extra-scientific factors, ultimately the researcher's interests were driven by "the internal history of the science in question". Merton attempted to delineate externalism and internalism along disciplinary boundaries, with context studied by the sociologist of science, and content by the historian. Historiographical approaches to theory change in science A major subject of concern and controversy in the philosophy of science has been the nature of paradigm shift or theory change in science. Karl Popper argued that scientific knowledge is progressive and cumulative; Thomas Kuhn, that scientific knowledge moves through "paradigm shifts" and is not necessarily progressive; and Paul Feyerabend, that scientific knowledge is not cumulative or