ABSTRACT
In the sixties, the concept of genetic disease was synonymous with the concept of monogenic disease: a rare inherited Mendelian mutation in one gene leads to one disease. Since then, a double shift has occurred in medical genetics. On the one hand, the concept of genetic disease has extended far beyond the model of monogenic disease, to the point where it can virtually apply to every disease, a process called “the geneticization of diseases.” On the other hand, the model of the simple monogenic disease has disintegrated and the distinction between monogenic diseases and polygenic ones has become more and more difficult to draw, to the point where there is no longer a consensual definition for the concept of genetic disease. This is what I call the “paradox of contemporary medical genetics”: every disease is considered genetic but no one knows how to define the concept of genetic disease. In this chapter, my aim is threefold. First, I will describe the history and the establishment of this paradox. Second, I will examine three philosophical answers that have been suggested so far in order to solve it and argue they are deeply unsatisfactory. Third, I will suggest a new way to solve the paradox.
