Philip Kitcher is one of the leading figures in the philosophy of science today. Here he collects, for the first time, many of his published articles on the philosophy of biology, spanning from the mid-1980's to the present. The book's title refers to Gregor Mendel, an Augustinian monk who was one of the first scientists to develop a theory of heredity. Mendel's work has been deeply influential to our understanding of our selves and our world, just as the study of genetics today will have a profound and long-term impact on future scientific research. Kitcher's articles cover a broad range of topics with similar philosophical and social significance: socio-biology, evolutionary psychology, species, race, altruism, genetic determinism, and the rebirth of creationism in Intelligent Design. Kitcher's work on the intersection of biology and the philosophy of science is both unprecedented and wide-ranging, and will appeal not only to philosophers of science, but to scholars and students across disciplines.