The pleasure principle is related to an idea that comes from economics and the attempt to predict markets and human buying behavior: the rational choice theory, embodied by the jokingly named Homo economicus. This states that all of our choices and decisions spring entirely from self-interest and the desire to bring as much pleasure to our lives as possible. It may not always hold up (otherwise market and stock prices would be one hundred percent predictable), but it provides more support for the simple nature of many of our motivations.
