This thesis explores the emergence of the concept of ethical responsibility in the writings of Dietrich Bonhoeffer (1906-1945) and Emmanuel Levinas (1906-1995). It argues that 'the other' and 'language' are both indispensable and correlative elements in the analysis of ethical responsibility presented by these two authors. Chapter one outlines the main theories of responsibility that have unfolded down in the history of philosophy to the twentieth century, noting the need to re-think the concept of ethical responsibility in light of the challenges offered by both Bonhoeffer and Levinas. Chapter two addresses the question that Bonhoeffer raises 'What is man?' in relation to the 'boundary' between the possibility and the limitations of man, taking into consideration the influence of Karl Barth's concerns on the Wholly Other and the Word of God on Bonhoeffer's 'non-religious interpretation of Christianity'. Chapter three analyses Heidegger's concepts of Dasein and language. Though inspired by Heidegger's reflections on the question of the meaning of Being in relation to the existential situation of human being, both Bonhoeffer and Levinas criticize Heidegger's Dasein analytic because it overlooks the role of 'the other' and 'language' in the ethical relation that exists between fellow human beings. Chapter four concentrates on Levinas' s thoughts on the responsible response via the exteriority of the face and the ethical significance of language, and argues that the response to 'what is the other?' is an answer to Bonhoeffer's question of 'what is man?' The fifth chapter argues that the ethical structure of responsibility is based on 'the Other' and 'language' as indispensable elements and applies this structure to a discussion of some central issues in religion, pluralism and Western-Chinese communication, re-enforcing the need to look again at the role of 'the Other' and 'language' in the ethical structure of responsibility.