This anthology continues the effort to make Kurt Lewin's work easily accessible again by bringing together 15 significant articles that were written over a span of 30 yrs. These articles were selected because they still stand as relevant contributions to the world's culture and they reflect the extraordinary range over which Lewin's intellectual activity remains relevant. The first several selections present Lewin as a philosopher of science. The next section includes original reports by Lewin of programs of research that he and his students, or colleagues, carried out on key theoretical problems in motivational, developmental, and social psychology. Following is a selection of articles that Lewin wrote as an applied psychologist. Last are sections in which Lewin responded to requests for advice from policymakers and community leaders.