This dissertation analyzes whether or not the principle of systemic integration - as expounded in Article 31(3)(c) of the Vienna Convention on the Law of Treaties - contributes to attainment of a coherent international legal system. For this purpose, the book considers three general ideas: the "unity" of the international legal system and fragmentation; the general rule on treaty interpretation and the principle of systemic integration; and the role of systemic integration in the achievement of coherence. Each one involves specific issues and considerations which ultimately assist in addressing the main question as to the usefulness of the principle in the curtailment of fragmentation in the international legal system. Dissertation. (Series: Cologne Studies in International and European Law / Kolner Schriften zum internationalen und europaischen Recht - Vol. 24)