This thesis makes a clear distinction between the relative influence of Hegel and Schelling on Tillich’s Systematic Theology, by focusing on the concepts of dialectic and the Trinity. It begins by calling into question the appropriateness of the method of correlation as a description of the structure of the Systematic Theology. It subsequently demonstrates that two different kinds of dialectic provide the actual structure of the Systematic Theology: a polar form of dialectic, which can be attributed to the influence of F. W. J. Schelling, predominant in the first volume of Tillich’s system; and a triadic form, attributable to G. W. F. Hegel, which provides the structure for all three volumes of Tillich’s system. Finally, it demonstrates the Hegelian influence on Tillich’s concept of the Trinity. This investigation is unique in three ways: in its argument that the method of correlation is not commensurate with what Tillich intends for the Systematic Theology; in its consideration of the Systematic Theology as a whole; and in its consultation of recent translations of the works of Hegel and Schelling, and recent English-speaking research into German Idealism.