What is the role of the church in a radically secular and pluralistic world in which science and technology set its course, while the prevalence of suffering constantly undermines its progress? This dissertation addresses the issue of the church and world relationship by an analysis of the development of Edward Schillebeeckx's thought on the issue. It makes two points: firstly, that the shifts in his theology express his consistent effort to see the church as sacrament always in relation to what it symbolizes, that is, God's salvation for humanity revealed in Jesus Christ; secondly, that Schillebeeckx found the church's unique role precisely in the relevance, communicability and credibility of its constructive and critical praxis in the world. To highlight continuity, this dissertation examines his multiple shifts, roughly divided into three periods: the period of his first major work, that of Vatican II, and that of his engagement with hermeneutics and critical theory. The linchpin of his continuity in discontinuity is sacramentality. From his early existential-phenomenological retrieval of Thomas Aquinas' theology of the sacraments to his unfinished work on the sacraments as 'metaphorical celebrations,' he pursued a dialectical synthesis of the church and the world. As his theology matured, it became less church-centered, more oriented toward the world, and critical of both the church and the world. The critical impulse came both from the 'foreign prophecy' of the world and from the Gospel on which he based the church's praxis of remembrance, actualization and eschatological hope. His developed view on the church and the world found expression in the dialectic of mysticism and politics. In the final chapter, this dissertation offers a case study of an ecclesial response to a controversial environmental project of the Korean government, to examine the implications of Schillebeeckx's theology for the church's role in the contemporary world. In conclusion, the value of the evolution of Schillebeeckx's view is assessed, and the strength of his developed thought reaffirmed, while some ambiguity and the need for further development are exposed in terms of the precise shape of the church's indirect but concrete involvement in the world of politics.