This thesis explores the varying discourses and concepts of ‘development’ used by those working in the development field, and the various biographical, institutional and macro-structural forces that shape them. It does so through a case study of missionaries and development workers from Ireland. Ireland’s history of engagement in development work provides an interesting case of ‘development work’ where missionaries dominated but have now been largely succeeded by a mix volunteers and professional development workers from a variety of occupational backgrounds, particularly in health and education. The uniqueness of the Irish development field according to the OECD (1999) is the direct contact the Irish field has with the developing world. It also reflects the unusual degree to which the Irish social services field has been characterized by religious and civil society (NGO) service provision, intertwined with that of the state. This profile is reflected in the social services orientation of Irish development work as well as the role of religious and civil society-based practitioners. Missionaries and development workers are immersed in a field which, according to Robert Chambers (2005, p.185), consists of “multiple realities - ecological, economic, social, political and personal”. These different realities are important because they structure the work and experiences of development. Thus, development workers and missionaries can experience and understand their work in different ways and in different realities, because “…who we are is formed by our admittedly fallible, reflections upon the world, meaning its natural, practical and social orders” (Archer, 2000, p.313). In the development field knowledge is stratified between theory and practice both running in parallel lines. In the midst of these literatures the place of religion has been neglected and the role missionaries as development practitioners has been overlooked. More recently, authors have examined the individual development practitioner, and their work has focused on development worker motivations, values, work and biographies to get a better understanding of who these actors are and how they go about their work. This thesis endeavours to contribute to these debates by examining the development discourses of Irish missionaries and development workers and investigating the process of learning that generates these discourses and that occurs in a variety of employment, occupational, biographical, political and regional contexts. This understanding of development is critically important as it shapes what kinds of development practices are thought to be reasonable and even ideal, and to whom they can be legitimately and ethically applied, and in which circumstances.