This thesis is a critique of Paul Tillich's ontology. It demonstrates inconsistency in Tillich's theological system, exposed by the microcosmic/macrocosmic theme, implicit in his theology. The thesis suggests that Tillich intuited the relationship between God and humanity in microcosmic/macrocosmic terms, but his tightly reasoned arguments stifled the intuition, causing the microcosmic theme to remain hidden under the more explicit concerns of his system. The thesis establishes the powerful microcosmic theme underlying Tillich's system, in which creaturely life is imbued with the Principles of divine life. This intimacy, coupled with inconsistency in Tillich's theology with regard to human freedom and estrangement, generates doubt about Tillich's assertion that creaturely estrangement from its divine ground is ontological in nature. In view of the fact that separation and estrangement are not merely idiosyncratic of Tillichian thought, but are entrenched in the western Christian tradition, the thesis looks outside that tradition to assess the validity of Tillich's claim with respect to the ontological nature of estrangement. To this end, the Chinese tradition is engaged, in order to ascertain the extent to which estrangement features in the ontology pertaining to a principal theme in that tradition, the Tao. In its exploration of the Tao through the two texts of the Lao Tzu and the Chuang Tzu, the thesis notes the absence of the theme of estrangement. In light of this, Tillich's insistence upon the ontological nature of estrangement is challenged on the grounds that if estrangement is truly ontological, it will be so for the whole of humankind, not solely for one particular tradition. Having shown Tillich's ontological assumption to be questionable, the thesis proceeds to consider the impact of the removal of the theme of estrangement from his system. It demonstrates that its removal not only permits the implicit microcosmic theme to be brought to the fore, but also transforms his theology from one based upon dualistic consciousness, with the inherent tensions and ambiguities that such awareness inevitably creates, to one based upon integration and holism. The thesis does not seek to offer a comparative study of the ontologies pertaining to Tillich and the Tao. Rather, it utilises the Tao as the means by which the researcher looks beyond Tillichian theology and the western tradition in which it was entrenched, in order to return to that theology with fresh insight. This is in accord with Tillich's own method of correlation, where he engages with that which lies beyond the finite creature, in order to gain fuller understanding of the nature of that creature.