Despite its long history, aid for poor countries has never had a secure ethical rationale. “Poverty reduction” is inadequate: I show that people who are equally poor, but in countries with different circumstances, should not be equally eligible. I ground the rationale for aid in two psychologically instinctive duties of rescue: for humanitarian aid the rescue is from catastrophe, for development assistance it is from mass despair. I argue that the common practice of making aid conditional upon policy—whether economic, as developed by the International Financial Institutions, or social and environmental as required by NGOs—is both unethical and counterproductive. Instead, I develop the advantages and limitations of aid for mutual benefit.