This collection of papers provides a commentary on and critique of Grotius' ""De Jure Pacs ac Belli"". It is the product of a joint research project on Grotius' book, carried out by the Research Group on the Fundamental Theory of International Law, headed by the editor.;An awareness among a group of young international law scholars in Japan of the need to reconsider the methodology and fundamental problems of international law led to the formation of the group in 1976. Its purpose is to carry out basic research on the theory of international law, including its validity as law, the normativity and rationalizing function of international law, and the relations between international law and, in particular, international politics, justice, war, structural violence and colonialism.;Through these researches, the group seeks to clarify its own views, to understand current problems of international law within their philosophical, political, historical and multi-cultural context, and ultimately to develop an approach which can overcome the defects of the so-called ""positivistic"" approach without reducing the science of international law to an ideology whose actual role is to justify the values, power position and interests of dominant states.;In an effort to achieve these objectives the group believes it is essential to understand classical writings that have influenced the development of modern international law against the historical background in which they were written. The group's first study is of Grotius' ""De Jure Belli ac Pacis libri tres"", long regard as (at least one of) the most important works in the development of international law, and engaged in a process of collective reading and study of the work over more than a decade.;In conjunction with it, ""The Future of International Law"" (edited by Richard Falk and Cyril Black), and also Pufendorf's ""De Jure Gentium et Naturae libri octo"". The further study plan will involve Vitoria, Vattel and other writers. The group's immediate aim is to attempt to reconstruct, or reconstrue, the history of modern international law. The problems to be investigated include positivism and international law, imperialism and international law, socialism and international law, the various regional ""world orders"" of the 17th, 18th and 19th centuries, and the globalization of European international law.