Democratic theorists increasingly stress that democratic legitimacy rests primarily on authentic deliberation. Critics of deliberative democracy believe that this hope is unrealistic - that deliberation either will prove intractable across political differences or will exacerbate instability. This paper deploys some tools of political psychology, notably Q methodology and values analysis, to investigate the conditions under which effective deliberation is likely to occur. These tools are applied to contemporary political debates in Australia, concerned with how the Australian polity should be constituted in light of a reform agenda underpinned by a discourse we term "Inclusive Republicanism." An investigation of the character of the basic value commitments associated with discursive positions in these debates shows that some differences will yield to deliberation, but others will not. When two discourses subscribe to different value bases, deliberation will induce reflection and facilitate positive-sum outcomes. When a discourse has a value base but finds its specific goals opposed by a competitor that otherwise has no value base of its own, deliberation will be ineffective. When one discourse subscribes to a value base that another questions, but without providing an alternative, deliberation can help to bridge idealism and cynicism.