The paper analyzes the early theory building process of Thomas Hunt Morgan from the 1910s to the 1930s and the introduction of the invisible gene as a main explanatory unit of heredity. Morgan’s work marks the transition between two different styles of thought. In the early 1900s, he shifted from an embryological study of the development of the organism to a study of the mechanism of genetic inheritance and gene action. According to his contemporaries as well as to historiography, Morgan (...) separated genetics from embryology, and the gene from the whole organism. Other scholars identified an underlying embryological focus in Morgan’s work throughout his career. Our paper aims to clarify the debate by concentrating on Morgan’s theory building—characterized by his confidence in the power of experimental methods, and carefully avoiding any ontological commitment towards the gene—and on the continuity of the questions to be addressed by both embryology and genetics. (shrink)

Stein has raised a fundamental problem for any attempt to characterize instrumentalism and realism as substantive alternatives. This is the distinguishability problem, which consists in the problem of developing a form of instrumentalism that is substantially different from a plausible realist alternative and the problem of showing that this form of instrumentalism does justice to actual scientific practice. Using Stein’s own discussion of Maxwell, I formulate instrumentalism and realism as a scientist’s attitudes toward models, where an attitude is understood to (...) be a complex of the scientist’s belief and intention regarding models. Developing a case study of Benzer’s modeling practice, I show that each attitude can structure inquiry differently and argue that to understand certain aspects of scientific practice, such as the practice of genetic mapping in Benzer’s work, we sometimes need to appeal to the coexistence of these attitudes. (shrink)

In this paper, I wish to challenge theory-biased approaches to scientific knowledge, by arguing for a study of theorizing, as a cognitive activity, rather than of theories, as abstract structures independent from the agents’ understanding of them. Such a study implies taking into account scientists’ reasoning processes, and their representational practices. Here, I analyze the representational practices of geneticists in the 1910s, as a means of shedding light on the content of classical genetics. Most philosophical accounts of classical genetics fail (...) to distinguish between the purely genetic, or Mendelian level, and the cytological one. I distinguish between them by characterizing them in terms of their respective associated representational practices. I then present how the two levels were articulated within Morgan’s theory of crossing-over, and I describe the representational technique of linkage mapping, which embodies the “merging” of the Mendelian and cytological levels. I propose an analysis of the mapping scheme, as a means of enlightening the conceptual articulation of Mendelian and cytological hypotheses within classical genetics. Finally, I present the respective views of three opponents to Morgan in the 1910s, who had a different understanding of the articulation of cytology and Mendelism, and entertained different views concerning the role and proper interpretation of maps. I propose to consider these diverging perspectives as instantiating what I call different “versions” of classical genetics. (shrink)