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 these roles are spelled out in terms of the representational practices in which these concepts are embedded. In particular, I will 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 a 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 will, by way of conclusion, briefly look at current developmental genetics. I introduce the topic of organismal characters by pointing out that characters are such an important category in the life sciences, as well as in broader social contexts, because the parts and properties of organisms they specify can be seen as the interfaces between human interests and organisms, including humans themselves. Since from the plurality of interests results a plurality of character concepts, I will 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. Representation will be characterized as having a systemic structure, in which alternatives of labels are coordinated with alternatives of referents. The notions of thick and thin phenomena that mark an important difference in character concepts, and the idea of syntactically and semantically dense or articulated symbol systems on which the distinction is based, will be introduced here. Furthermore, a notion of practice will be developed that relates actions to symbol systems. Chapters 4, 5, 6 and the Conclusion contain the discussion of the character concepts in the disciplines taken into consideration.