Altruism is a human disposition to care for the other. It keeps the community together, but it can also be a vulnerability easily exploited for other purposes. Various social conditions contribute to the suppression of critical thinking: religious traditions and ideologies, unselfishness, ethics of convictions. The lack of critical systems thinking hinders us in being responsible and effective altruists. Rational thinking motivates us to evaluate the quality of the NGO, and the relevance and quality of its presented projects. Criteria are discussed which enable managers and project designers to sort out and appreciate the measurable from the likely immeasurable impact of an intended intervention in a social system in its wider context. These criteria allow potential donors to evaluate and decide whether or not to invest in a given project. By supporting or withholding one's contributions, the benefactor may press the NGOs and project leaders to act more as responsible and effective altruists, while behaving oneself as a responsible citizen.