The student or practitioner whose interest is primarily in the interpretation and application of the law of nations is often prone to dismiss fundamental concepts as a matter of mere theoretical importance. This is a serious mistake. No one is capable of understanding the interpretations and applications of the law of nations which have been made in judicial decisions, national and international, in arbitrations, and in international incidents, unless he has some knowledge of the fundamental concepts of the science and of the conditions under which those concepts have developed. Concepts, in truth, are as much a part of the fabric of international jurisprudence as the intricate and confused records of international conduct. If they are no longer its warp and woof, they provide at least the necessary patterns.