There has recently been much debate about the idea of levying a tax on particular transactions on international financial markets. Economists have argued about how much revenue such an international financial transaction tax would raise and they disagree about what effects it would have on trade volumes, financial stability, and overall growth. Politicians have argued about the feasibility of introducing such a tax internationally and they disagree on its adequacy as a policy response to the current financial and economic crisis. (...) This article contributes to the debate about international financial transaction taxation by bringing the perspective of political philosophy to bear on the politicians’ and economists’ arguments about policy. I shall outline a framework for thinking about justice in finance, and defend the idea of an international financial transaction tax as an instrument for making the international financial system more just. (shrink)