This collection of articles and essays embodies a new approach to sociology based on the original meaning of the word. Its central concept is "community," which is defined to cover units as small as the household and as large as the nation-state. Individuals are a special case of community. So defined, communities account for almost all the independent social organization of the planet. At every level, communities must deal with unpredictable threats from nature, other communities and internal conflict. Success in this effort, as measured by indicators of average health, depends on the...