The biological and philosophical implications of the emergence of new collective individuals from associations of living beings. Our intuitive assumption that only organisms are the real individuals in the natural world is at odds with developments in cell biology, ecology, genetics, evolutionary biology, and other fields. Although organisms have served for centuries as nature's paradigmatic individuals, science suggests that organisms are only one of the many ways in which the natural world could be organized. When living beings work together-as in ant colonies, beehives, and bacteria-metazoan symbiosis-new collective individuals can emerge. In this book, leading scholars consider the biological and philosophical implications of the emergence of these new collective individuals from associations of living beings. The topics they consider range from metaphysical issues to biological research on natural selection, sociobiology, and symbiosis. The contributors investigate individuality and its relationship to evolution and the specific concept of organism; the tension between group evolution and individual adaptation; and the structure of collective individuals and the extent to which they can be defined by the same concept of individuality. These new perspectives on evolved individuality should trigger important revisions to both philosophical and biological conceptions of the individual. Contributors Frederic Bouchard, Ellen Clarke, Jennifer Fewell, Andrew Gardner, Peter Godfrey-Smith, Charles J. Goodnight, Matt Haber, Andrew Hamilton, Philippe Huneman, Samir Okasha, Thomas Pradeu, Scott Turner, Minus van Baalen