This book in its entirety as well as in each of its parts is an outline of the problems under discussion. The subject matter of some eighty sections of the book is extensive; it could, indeed, be presented by ex- perts in as many volumes. This study offers an attempt to formulate a synthesis, however difficult, of the vast amount of available material. Unlike the well-known standard Introductions to International Law which deal with all the major fields of international law, this book treats exclusively the present conceptions of that law as expressed in legal literature, international treaties and other agreements, inter- national judgements and awards, governmental and diplomatic state- ments and the like. Special attention is devoted, in several chapters of the book, to the "teachings of the most highly qualified publicists of the various nations" which are considered by Article 38 paragraph 1 (d) of the Statute of the International Court of Justice as "subsidiary means for the determination ofrules of law. " An endeavor is made to ascertain whether in certain fields of the theory of international law a "Communis opinio doctorum" has either been reached or is in the process of achievement. Some readers may consider that there are too many quotations from writings of publicists; others will certainly feel - as does this writer - that too many outstanding international lawyers have not been included.