International finance is often understood to be a rational practice, taking place within an autonomous, coherent and clearly bounded structure. This thesis questions the naturalness implied by such understandings of the international financial system. It argues that the contingencies and ambiguities of financial history have been largely written out of the discipline of International Political Economy (IPE) in general and the study of international finance in particular. The thesis presents a detailed account of the conceptual histories that enable us to think of a domain called finance. It does so in terms of a 'genealogy,' the concept offered by French philosopher Michel Foucault to denote a historical study that resists being a linear and frictionless account of the emergence of modern practices. A genealogy of finance discusses the continggeenntt emergence of fi'n ancial thought, thus arguing that no logical or evolutionary trajectory for the development of fi' nancial rationality was implicit in history or human nature. The thesis analyses a range of archival materials debating the emerging fin ' ancial sphere in London and NewYork, beginning with the birth of the credit economy in seventeenth-century England and proceeding into to the 1990s. The analysis' looks at political contestations over understandings of time and money, the gendered discourse of credit and credibility, the proper meaning of the free market, understandings of financial crisis, the morality of speculation, the differences between gambling and fin' ance, and the imagination of fi' nance as a rational and scientific practice. The thesis emphasises how these political controversies assume, in' yoke and debate a subject called 'fin ' ancial man.' The debates analysed in this thesis have shaped the regulatory and institutional structures of modern in ' ternational fin ' ance. In an era when fin ' ancial practices are closed off from democratic politics through the assertion that fin' ance is too specialist for broad-based public debate, the exposure of contingencies and ambiguities in financial practices must be regarded as a political critique.