This paper presents the idea of nature in Tillich's earlier theological and philosophical writings and attempts to discuss its significances for an ecological approach to our environmental crisis. The paper consists of four parts. The first part explores the appropriation of Schelling's philosophy of nature in Tillich's thought and shows the idealistic and romantic characters in Tillich's conception of nature. The second part discusses the concept of "belief-ful realism" (gläubiger Realismus) in order to disclose the realistic approach in Tillich's thought. The third part shows the ambiguity of technology in Tillich's perspective. Last part explores Tillich's understanding of the relationship between history and nature.