Do you want to know a dirty little secret of economists who give policy advice? When we do so, we are often speaking not just as economic scientists, but also as political philosophers. Our recommendations are based not only on our understanding of how the world works, but also on our judgments about what makes a good society.

The necessity of political philosophy arises because most policies are good for some people and bad for others. For example, an increase in the minimum wage, as proposed by President Obama, may raise incomes for some low-wage workers, but it will cause some businesses to make smaller profits, some customers to pay more and some workers to lose their jobs.

Similarly, the Affordable Care Act has provided greater opportunity for some people to get health insurance, but it also caused cancellations for others who were previously happy with their insurance. Evaluating the overall effect of these policies requires balancing competing interests.

To strike this balance, many economists think in terms of a “social welfare function” that aggregates individuals’ well-being into a summary measure. This approach dates back to the utilitarian philosophers of the 19th century, such as Jeremy Bentham and John Stuart Mill. The utilitarians suggested that each person in society receives a certain amount of happiness, or “utility,” from an allocation of society’s resources. The job of policy makers, they argued, is to do their best to maximize the total utility of everyone in society. According to utilitarians, taking a dollar from Peter and giving it to Paul is justified if Peter’s decrease in utility is smaller than Paul’s increase, as would plausibly be the case if Peter is richer than Paul.