THICK AND THIN CHARACTERS:ORGANISMAL FORM AND REPRESENTATIONAL PRACTICE IN EMBRYOLOGY AND GENETICS

In this thesis the family of concepts, including characters, traits and phenotypes of organisms is analyzed according to the various roles these concepts play in different disciplines and in different historical periods. The ways the concepts are construed in order to fulfill their roles are spelled out in terms of the representational practices in which these concepts are embedded. In particular, I look at classical genetics in the period spanning from Mendel to Morgan and compare the character concept that gradually developed in this period – and which I characterize as a thin concept, meaning that characters appear as values of variables that are represented in articulated symbol systems – with the thick concept of parts, properties and processes as it prevails in anatomy, physiology and embryology. In order to illustrate that both concepts still play their role in modern biology and to address the question of their possible integration, I conclude by briefly looking at current developmental genetics. I address the general issue of scientific pluralism in Chapter 1. Chapter 2 and 3 introduce the methodological concepts necessary to analyze the representational practices that embody the various character concepts. Chapters 4, 5, 6 and the Conclusion contain the discussion of the character concepts in the disciplines taken into consideration.