The Principia Cybernetica Project was created to develop an integrated philosophy or world view, based on the theories of evolution, self-organization, systems and cybernetics. Its conceptual network has been implemented as an extensive website. The present paper reviews the assumptions behind the project, focusing on its rationale, its philosophical presuppositions, and its concrete methodology for computer-supported collaborative development. Principia Cybernetica starts from a process ontology, where a sequence of elementary actions produces ever more complex forms of organization through the mechanism (...) of variation and selection, and metasystem transition. Its epistemology is constructivist and evolutionary: models are constructed by subjects for their own purposes, but undergo selection by the environment. Its ethics takes fitness and the continuation of evolution as the basic value, and derives more concrete guidelines from this implicit purpose. Together, these postulates and their implications provide answers to a range of age-old philosophical questions. (shrink)