Whereas states formerly had a right to wage war under a wide range of cicumstances, now war is legally permitted only in self defence. Yet wars persist. If their incidence is to be reduced, we must understand the forces that maintain war as an institution. The contributors to this book consider the nature of war and the forces that sustain it from diverse perspectives ranging from anthropology, history, political science, theology, philosophy, international law, economics, psychiatry and biology. The complexity of modern war requires understanding not only of several layers of social complexity - individuals, groups, societies - but also of the dialectical relations between those levels. This implies that individuals can contriburte towards a reduction in wars incidence.