This anthology collects some of the most important papers on what is believed to be the major force in evolution, natural selection. An issue of great consequence in the philosophy of biology concerns the levels at which, and the units upon which selection acts. In recent years, biologists and philosophers have published a large number of papers bearing on this subject. The papers selected for inclusion in this book are divided into three main sections covering the history of the subject, explaining its conceptual foundations, and focusing on kin and group selection and higher levels of selection.One of the book's interesting features is that it draws together material from the biological and philosophical literatures. The philosophical literature, having thoroughly absorbed the biological material, now offers conceptual tools suitable for the reworking of the biological arguments. Although a full symbiosis has yet to develop, this anthology offers a unique resource for students in both biology and philosophy. A Bradford Book.