  Some philosophers defend extremely demanding and far-reaching principles of obligatory beneficence. Peter Singer’s theory has been the most widely discussed account. Singer has throughout his career been interested in how to reduce the evils of global harm and suffering in the most effective manner. In his early work, Singer distinguished between preventing evil and promoting good and contended that persons in prosperous nations are morally obligated to prevent something bad or evil from happening if it is in their power to do so without having to sacrifice anything of comparable importance. The argument is that serious shortages of housing, food, and healthcare are harmful to human life and welfare and are preventable. If person P has some capacity to prevent these evils—for example, by donation to aid agencies—without loss of comparable item(s) of importance, P acts unethically by not contributing to the alleviation of these shortages. Accordingly, in the face of preventable disease and poverty we are morally obligated to donate time or resources toward their eradication until we reach a level at which, by giving more, we would cause as much suffering to ourselves as we would relieve through our gift. This demanding principle of beneficence requires us to invest heavily in rescuing needy persons in the global population; merely donating at the level of local communities and nation states is insufficient. However, Singer leaves it open what counts as being of comparable importance and as being an appropriate level of sacrifice.