This thesis is a unique and original application of grammatical reading, Véronique Pin-Fat's applied interpretation of Ludwig Wittgenstein's philosophy of language, to the relief and reconstruction field. Countries emerging from conflict have become international priorities, with increased interest in 'failed states' following the terrorist attacks of 11th September 2001. Non-governmental organisations have been central to this process, providing interventions with legitimacy. However, these interventions have failed to deliver international security and have received much criticism for the Western 'liberal peace' agenda that they pursue. There is a growing appreciation of the need to interrogate not just practices of relief and reconstruction but the assumptions which underlie them.This thesis suggests an approach which takes language as the unit of analysis can help us to bring assumptions to the fore. Grammatical reading explores the relationship between language and reality through the metaphor of language games, where meaning is controlled though grammar. Grammar controls possibility in language games by determining what it is possible to say and do and remain intelligible. This allows us to think differently about how possibility is shaped through our language use, in particular, by allowing us to interrogate the linguistic construction reality. Looking in detail at the example of Oxfam's practices of relief and reconstruction in South Sudan by examining the grammatical constitution of three sets of 'pictures' - subjectivity, space and security - grammatical reading enables explore how the organisation has drawn lines it its language between possibility and impossibility which have material and political consequences. The thesis will argue that each of Oxfam's pictures was an example of grammatical failure. Oxfam's picture of subjectivity, produced by a grammar of capacity/incapacity, led it to a paternalistic relationship, in which it was instructing a deficient South Sudan, whilst indefinite international aid was deemed essential. Oxfam's pictures of space were produced through a grammar of promise/danger and prevented the organisation from envisaging a South Sudan not beleaguered by crisis. This was functional for Oxfam, as the organisation saw crises as moments of opportunity for change and expansion of its activities in the country. Finally, in Oxfam's picture of security, the organisation's grammar of security/vulnerability meant that the organisation elided development and security. This was problematic as each was seen as a condition of possibility for the other to occur, making both grammatically (im)possible. Furthermore, the organisation's elision of security and development meant that it found itself implicated in the very security discourses it sought to criticise. The thesis concludes by arguing that this failure reminds us of the need to engage with the political. In the space that failure provides we can question how particular ideas about possibility have been constructed, how they have achieved the status of knowledge and what the effects of this are for practices of relief and reconstruction.