Carbon offsetting has been an institutionalised response to climate change for over a decade. Over this period, climate change has become more severe and calls for climate justice have become increasingly insistent. Yet the normative controversies of carbon offsetting remain unresolved, as debates about the environmental quality, development impacts and ethical implications of carbon offsetting continue. This thesis explores the relationship between morality and carbon offsetting in three domains. First it provides an evaluation of the ethics of offsetting. Second it gives an account of the 'lay normativity' of the market, describing how carbon market actors interpret and act upon issues of moral concern. And third, it explains offsetting's moral economy. First, the thesis examines the moral rationales for and problems of offsetting in order to clarify the bases of criticisms levelled at offsets by researchers concerned about trends in neoliberal environmental governance. In evaluation of the ethics of offsetting, the PhD recognises some limited rationales, but mainly highlights widespread problems including lack of environmental integrity and failure to produce 'sustainable development'. The structure of the market is shown to create opportunities for malpractice and difficulties for reform. Second, building on work in cultural political economy, the research describes carbon offsetting's lay normativity. The account is based on interviews with over sixty carbon offset market actors including project developers, consultants, auditors, regulators, retailers and buyers in the UK, continental Europe, and in India. Findings show that the market is founded on ethical principles: offsetting is nothing without notions of environmental and developmental care. Critiques of, and reforms to, offsetting are also grounded in principled debate. But carbon market actors often use their power to further commercial interests that are not aligned with production of environmental or developmental value. And yet, even as rationales are ignored and problems are amplified, market actors maintain a discursive semblance of moral behaviour through forms of justification, story-telling and identity work. Third, the thesis explains how principles, profit and power combine to affect the governance of offsetting. It shows that the concentration of power among profit-seeking actors drives the production of offsetting's moral problems in the stages of project development, regulation and retail. Commercial interests in the politics of knowledge lead to manipulation of the discursive framings through which people come to understand offsets. Ethical narratives are deployed to sustain the market in states of dysfunction, enabling privileged groups to gain exchange value at the expense of climate protection and sustainable development. Through this explanatory work, the PhD contributes an original application of ideas about moral political economy to the case of climate change and carbon trading, demonstrating that powerful actors can shape culture and alter our perceptions of right and wrong.