As Peter Singer writes in his book The Life You Can Save: "[t]he world would be a much simpler place if one could bring about social change merely by making a logically consistent moral argument". Many people one encounters might agree that a social change movement is noble yet not want to do anything to promote it, or want to give more money to a charity yet refrain from doing so. Additional moralizing doesn't seem to do the trick. ...So what does?
Motivating people to altruism is relevant for the optimal philanthropy movement. For a start on the answer, like many things, I turn to psychology. Specifically, the psychology Peter Singer catalogues in his book