This thesis seeks to analyse the intellectual contribution of James Bronterre O'Brien to working-class anti-capitalist political economy, while placing it in its true historical and intellectual context. In so doing, the thesis aims to fill significant gaps left by O'Brien's biographer, Alfred Plummer, who dealt only cursorily with O'Brien's ideas. In contrast to past accounts of O'Brien, which tended to analyse him purely in terms of his significance vis-a-vis Marx, the thesis considers O'Brien's work on its own terms, analysing both its continuities with early nineteenth-century anti-capitalist political economy, and the significant ways in which it marked a break from previous work. In particular, the thesis argues that O'Brien evinced a uniquely broad vision of the role democracy would play in the post-capitalist society; for in O'Brien's new society democracy's remit was to extend far beyond Parliament. Further, O'Brien took the nascent class analysis of Hall and others, and constructed his entire political economy on the basis of a mature, and fully elaborated, antagonistic class model. The originality of his analysis, it is argued, is intelligible only if sufficient attention is paid both to the historical moment at which O'Brien began writing, and to his intimate connection with the `Political Owenism' of Henry Hetherington and others within organisations such as the NUWC. The concept of class allowed O'Brien to combine Owen's environmentalism with the demonology of older, Cobbettite radicalism. He was thus able to formulate a political economy which spoke to workers in a language with which they were familiar, but which was also more relevant to the social and economic realities of 1830s Britain. The thesis also considers the evolution of O'Brien's vision of the good life during the 1830s and after, and argues that O'Brien's relationship with his imagined audience is the crucial factor in this regard. From 1841, a break occurred, with O'Brien now oscillating between his old analysis and a liberal political economy criticising excessive taxation etc. rather than capitalism per se. The reasons for this shift, and for O'Brien's eventual abandonment of democracy in the late 1840s, are also explored