Though it is not at the centre of political attention Citizen's Income (CI) receives the kind of widespread ideological support which most other proposals in the area of labour market and social security reform do not. Given the breadth of such support the objective of this research is to improve understanding of why various ideologies get involved in the debate and of how the differing ideological forms of CI subsequently evolve. Chapter 1 introduces the debate and the research while chapter 2 outlines the principal ideologies with which the thesis deals. Chapters 3 to 5 then address those subjects - citizenship, work and full employment - which are at the heart of disagreements over benefit reform, since it is here that ideological distinctions relevant to the welfare state begin to be made. This approach allows us to formulate those principals which our varying ideologies would have a CI serve. Chapter 6 then examines Negative Income Tax as that form of CI most likely to be supported by economic liberals. Chapter 7 analyses why social democrats are attached to the principle of social insurance and why this might lead them to support a combination of CI and insurance benefits, i.e. a Participation Income. Chapter 8 looks at the importance of a social dividend to any market socialist strategy of the democratic Left and chapters 9 and 10 examine, respectively, ecological and feminist justification of CI, partly in their own right and partly as critiques upon which the democratic Left must draw. In the concluding chapter I argue that the widespread ideological support for CI is largely of a negative kind, i.e. a set of distinct but complementary reactions to the failures of non-integrated tax and benefit systems. Should CI enter the mainstream of policy-making debates then this consensus might well break down since disagreements over the generosity and the (un)conditionality of any CI would inevitably become more important.