The first half of this thesis delineates two different dialectical approaches present in Paul Tillich's Systematic Theology, which help shape both the structure and the Trinitarian content of the system. The first is a polar form of dialectic, present largely in the first volume ofthe Systematic Theology, which helps shape Tillich's dialectical ontology of being and non-being, and which closely resembles the dialectical approach of F.W.J. Schelling. The second is a triadic form of dialectic, observable throughout all three volumes ofthe Systematic Theology, which helps shape Tillich's existential description of salvation and history in terms of essence and existence, and which suggests a heretofore unexplored resemblance to the dist...