It is fair to say that self interest, as a human motivation, is almost universally regarded with disdain. We like to believe that our intentions go beyond the self. Surely the choices that human beings make, economic and non-economic, are sometimes driven by altruism and by ethics. Self-interest maximization is too narrow and too crass a motivation to explain the great variety and depth of human behaviour.

This line of argument is incorrect because it is based on a misunderstanding of the concept of self interest. In a real sense, rational self interest must be the driving force behind human decision making. And this is true of non-economic as well as economic behaviour. If people are free to make their own choices, then whatever choices they make must, from their perspective, maximize their own interest, otherwise they would not have chosen them. The choices we make necessarily further our own interest.

But what about the decisions we make that appear to serve the interests of others, sometimes at a cost to ourselves? For example, what about the decision of someone to give money to a friend or to a charitable cause? What about the decision of a parent to sacrifice for her children? And what about the business executive who volunteers time and money in the service of his church? Surely we cannot attribute these virtuous acts to so grubby and unworthy a motivation as rational self interest.

But we can maintain that these and all other similar good and virtuous behaviours are driven by self interest. Helping others in our society makes us feel good. Kind acts improve the well-being of the giver as well as the receiver. It is an intrinsic part of our humanity to take pleasure from the happiness of others. And a good thing, too! For such acts are the glue of social order.

Adam Smith was one among many moral philosophers who observed this important human characteristic. In the Theory of Moral Sentiments, Smith wrote:

How selfish soever man may be supposed, there are evidently some principles in his nature which interest him in the fortunes of others, and render their happiness necessary to him, though he derives nothing from it, except the pleasure of seeing it.

In the language of economics, we can say that the well being of other people (some more than others) is a factor in my "utility function." My utility is improved whenever the well-being of certain others is improved. But there is more to it than this. My well being is also improved by knowing that others in society have a favourable impression of me. This provides another self-interested reason for compassion. Additionally, some people believe that there are heavenly rewards to charitable and virtuous acts.

The point, then, is that any choice made by human beings is necessarily driven by self interest. Other supposed motivations such as altruism or "ethics-related" influences are a fiction, or at best, are a subcategory of self interest. We—all of us—are self-interest maximizers. We cannot do otherwise.

While virtuous acts are fully consistent with self interest, it is not true that all behaviour driven by self interest is necessarily good and virtuous. For some people, theft of the property of others may well maximize self interest. For others, a physical or sexual assault may serve their interest. We recognize that some actions may be deliberately or accidentally harmful to others in society. We have rules, customs, and formal laws (along with a variety of punishments) which take into account the harm people may do to others. These constraints, ideally, become part of the `black box' out of which decisions and choices emerge.

A common view of self interest is that it is a motivation unworthy of human beings. It is equated with narrow selfishness and reflects, at the very foundation, what is wrong with free market capitalism. For those who hold this view, there is a clear dichotomy between decisions based on rational self interest and decisions based on ethics. The two are apparently not compatible. I wish to reject this view categorically. With Smith, I see human beings incorporating ethical considerations into their decision making automatically. I observe formal and informal sanctions as important considerations constraining choices. For most people most of the time, self interest works well to prevent antisocial behaviour. And, as Smith also noted in the Wealth of Nations, in a relatively free society, the result of the full expression of self interest is economic prosperity. I quote:

It is not from the benevolence of the butcher, the brewer or the baker that we expect our dinner, but from their regard of their own interest. . . . The natural effort of every individual to better his own condition, when suffered to exert itself with freedom and security, is so powerful a principle, that it is alone and without any assistance [capable] of carrying on the society to wealth and prosperity.