Many different factors influence our health prospects. The food we consume, the lifestyle we live (e.g., sedentary or active), our economic prospects, our love prospects, our gender, our age, and our education all influence our expected lifetime acquisition of what John Rawls calls the “natural primary goods” (e.g., health, vigor, imagination, and intelligence). Our well-being is also influenced by the natural endowments we inherit from our parents. All people have two copies of most genes, one from their mother and one from their father. Genes are the fundamental physical and functional unit of heredity; they “specify the proteins that form the units of which homoeostatic devices are composed.”Earlier versions of this paper were presented to the Department of Philosophy at the University of Waterloo, the James Martin Advanced Research Seminar at Oxford University, and the Department of Politics at Manchester University. I am grateful for the helpful feedback that I received on those occasions.