Function, dysfunction, and disease in biology and medicine

In this dissertation, I explicate the concept of function in biology and explore how ideas about natural selection play a role in justifying function claims. In addition, I show how the understanding of function can be used to clarify concepts of dysfunction and disease in biology and medicine.;Much of the discussion of function over the last 25 years has revolved around a debate over the etiological view, which claims that in order for a trait to have the function F it must have been favored by natural selection for doing F. In Chapter One, I describe the two sides in this debate and how the conception of this philosophical project has evolved. Along with others, I argue that there is a place for etiological and non-etiological concepts of function in biology, although I undermine previous accounts of the relation between these concepts. In Chapter Two, I critique the view that natural selection designs living things or solves problems that species face, a view which has been associated with the etiological approach. I describe how we can explain a trait's natural selection without appealing to such problematic teleological ideas.;The current etiological account of function called the "modern history" view has added the requirement that the relevant natural selection must have occurred in the recent past. Although this solves some problems the etiological view faced, it also encounter problems of its own, described in Chapter Three. I present my own version of the etiological view, which avoids these problems. In Chapter Four, I critique the popular idea that there are exactly two concepts of function in biology---defined by an etiological and a non-etiological account---and argue that a more complex set of concepts is at work.;Finally, in Chapter Five I define concepts of dysfunction and disease based on the improved understanding of the idea of function. In this way, I describe how the philosophical understanding of teleology in biology can inform debates over the concept of disease in medicine.