This introductory volume to the series of American Classics in International Law is intended to present, put into context, and critically appraise specifically American general theories of and about international law. Those frameworks of ideas include the very concept of international law, its justification, the struggle between formalism and experience, various theories of legitimacy and fairness, the law’s effectiveness, empirical analysis, critiques from the margins and the center, and approaches to its improvement. Particular focus is on American Legal Realism, the New Haven School of Jurisprudence, International and Transnational Legal Process, liberal theories of international law, linkages to social sciences, including Law and Economics, Critical Legal Studies, LatCrit, TWAIL, and feminist approaches to the discipline.