Due to its influence during the Reformation, a substantial literature on the concept of vocation exists in the disciplines of history, sociology, and theology, but there is a relative paucity of writings on vocation from the perspective of ethical theory. This study seeks to address this gap in the literature by developing a typology of four ethical approaches to the concept of vocation: vocation as divine command, which understands the call as a person-relative command from God; vocation as natural order, which considers vocation as one's position within a divinely-ordained social order; vocation as self-actualization, which sees vocation as the actualization of a divinely-given personal essence; and vocation as election, which sees vocation as the call to belong to a chosen community. As a means to clarifying the four types, this study focuses on four figures—Søren Kierkegaard, Emil Brunner, Max Scheler, and Karl Barth—whose writings on vocation exemplify the types and illuminate the theological commitments that undergird them. The focus of each treatment is twofold: both to describe the author's theory of vocation and to examine the pattern of thinking it represents. For each author, the study highlights the theological assumptions that inform his concept of vocation, as well as its characteristic strengths and weaknesses, taking care to distinguish those features that are essential to the type and those that belong to the exemplar. The dissertation concludes by outlining three constructive strategies for integrating the four types into a more comprehensive theory of vocation.