Those seeking to understand attitudes to decentralization focus on attitudes to constitutional change or to the ideal level of government to control particular areas of jurisdiction. Within this is a wider approach to understanding subjective dimensions of multi-level states and the different communities of interest or polities that exist within them. Drawing on data from successive rounds of the Future of England (including parallel surveys in Scotland and Wales), this article develops a conceptual framework through which to understand political unions as well as a multi-dimensional measure through which to evaluate the location of unions from a scale that runs from subjective unionism to subjective autonomism. It outlines the various unions of the mind, including an identity union, a union of economic solidarity, of social solidarity and of fairness (or legitimacy) and then proceeds to map these within the UK. It then evaluates what impact each of these has on attitudes to the wider state, including attitudes to its continued survival. The article draws primarily on individual-level survey data collected by the authors but refers also to campaigns for constitutional change in unions and relates this to what we know about how individuals conceive of the states in which they live.