The paper is devoted to one of the key topics in the work of the outstanding German-American philosopher and theologian Paul Tillich (1886-1965), which is an interrelation of philosophy and theology. In the 20th century, the problem of the relation between philosophy and theology was posed with new urgency, which forced thinkers to turn back to the origins of Western civilization and to reconsider philosophy's dual descent from Parmenides' and Heraclitus' "true being" and from the revelation of the God of Moses, the Prophets and Christ. It is not the author's aim to discuss the historical background of the problem of interrelation of philosophy and theology, traditional for the European thought since II century AD; she would rather seek to clarify the philosophical and theological tradition to which Tillich belongs, and to demonstrate with precision what is new in his approach.