What is a cell type? – CELLTYPE

Classifications are fundamental conceptual tools for the systematization of scientific knowledge. Some classification systems, such as the periodic table of elements, are thought to reflect the structure of the natural world rather than the interests of human beings and result in "natural kinds”. Philosophers have debated whether natural kinds also exist in biology, generally considering classifications of organisms. Cell types have not received much attention in this context, although they are arguably also fundamental to many areas of biology and raise philosophical questions beyond those found in debates about standard examples. Many biologists seem to tacitly assume that different criteria coincide and result in an objective classification of cell types. However, recent research suggests a more complex picture where cellular phenotypes are much more plastic and heterogeneous than previously assumed. These developments have made the notion of cell type, which has never been clearly defined, very problematic. The aim of this project is thus to clarify the concept of "cell type". In particular, it puts forward two hypotheses: 1) The different criteria, apparently in conflict, can be aligned when explicating their conceptual relationships, suggesting a monistic notion of cell types as "functional species". 2) The new findings do not lead to a conceptual revision of this notion, but rather to a revision of factual knowledge about cell types. The project applies philosophical tools of conceptual analysis and definition and is based on a careful reading of the scientific literature and close interaction with biologists.