Economists' view of the world
Remember, economists view the world, at least the economic world, as a mechanical system. This view can be diagrammed in black and white. Many economists believe that while they may not completely understand the system, it exists in a pure and predictable form. That is, they 're not going to create it: they are going to continue to discover how it works. Their assumptions are based on the belief that there are principles upon which the world and the universe operate which are pretty much unchanging. This belief comes from the development of what are called "hard sciences" like physics and chemistry where scientists make observations and test them and then conclude that they have found phenomena that are predictable, like gravity or the rotation of the earth on its axis. Since we humans are also phenomena of the universe, the assumption is that we, too, follow predictable rules even if our spouses don't think we do. Efforts to find timeless rules for human behavior using what the scientific method have led to the development of the "soft sciences" like economics, political science, sociology and social psychology. I would agree with people who also think the study of humans acquired a scientific veneer because beginning in the nineteenth century, people tended to overuse and overvalue scientific approaches to learning at the expense of more subjective ones. Thus, to gain respectability, people interested in human development found it necessary to frame their investigations in the language of science.
This is not really bad when scientific tools of observation and measurement are not the only tools valued, but it is when they are the only ones. Today, in our country at least, this is what has happened so that we see art and literature devalued into fringey subjects, not things kids should learn about or from in school, and we see the emphasis put on only what is "practical." In fact, art and literature and theater and education now are framed in economic terms and seem to have to hold their own as simply economic products. When a city decides it really needs its symphony orchestra as San Antonio, Texas has, its argument for funding it is that it will "attract business." The new head of the symphony was hired because he would incorporate "good business practices" with the hope that the symphony by itself would turn a profit, necessary to continue justifying its support.
Another negative consequenceof our devotion to the soft sciences not just of economics but of sociology and others is that we allow ourselves to be driven by what is not even good soft science: poorly tested hypotheses become driving forces in our culture: for instance, how our culture uses the concept of self-esteem.
While there is great value in a "social science" or "soft science" approach to some human problems, it is an approach which, if universalized, deprives us of awareness of much that is inherent in our nature.
So what does all this have to do with economics? Economics is a "soft science." Like other soft scientists, some economists think they are working in a "hard science." They push and pull at the systems they perceive but do not really question whether the system as they see it actually exists. The pushing and pulling makes things happen within the system they have defined, but that system excludes many of the forces shaping people, cultures, the physical environment of the world and also blinds them to the consequences of pushing and pulling within their system. More seriously, we've generalized their system and turned it into dogma. Thus, in U.S. we have running our government people who might be called economic ideologues.
So. Let's look at how human beings are defined in economics.
Most basically, economists think that humans act rationally. This doesn't mean that we would all agree that each others' decisions are sensible or smart, but rather that within the context of each person's mind, she is making a rational choice. And our lives are, in this context, always a series of choices. We choose whether to get out of bed each day, for instance. When we make our choices, we do so bydeciding which decision is better according to our values and prioritizing. So when the alarm goes off, we might decide we can snooze for another ten minutes. If we do that, maybe we've asked ourselves (almost without thinking about it) whether we value some more dozing more than we value getting up and getting ready for work right away. We would consider things like whether we would be late or not, whether the pleasure of the sleep outweights the pleasure of a cup of coffee right away, and so on.
Generally, economists and many other people assume that this rational decision making for choosing alternatives is always establishing priorities for the use of time and money or even just money: a human being as homo economicus That is, that every person's decisions, whether made consciously in these terms or not, could be quantified in terms of money.
Today economists are not so simple-minded as to say that every decision people make is exclusively in one's own self-interest. There is room for altruistic decisions and for group decisions. But they would say that it is still an individual's rational decision to accept a group's decision.
In the United States, official economic thought is dominated by free market economists, perhaps ironically considered liberals. These economists and the politicians they influence and the businesses that benefit from free market ideology consider that humans are homines economici and that freedom is the freedom to make rational economic choices: therefore, the government should not in any way interfere with the freedom of the market so as not to interfere with a person's freedom to make market choices, the true meaning of freedom. This is an extreme view in the larger world.
Remember, underlying this homo economicus the idea of people's choices always being rational, even if they might not all have economic implications. Thus, today even in the United States there are efforts to enlarge the definition of the rational choices people make. There is still not too much attention paid to the idea that some choices may be completely irrational and that completely irrational choices may have a larger effect than on the individuals making them.
Some articles I referred to for the information on homo economicus:
McCaffery, Edward J and Siemrod, Joel (2004): "Toward an Agenda for Behavioral Public Finance" in University of Southern California Law School: University of Southern California Law and Economics Working Paper Series
Mertinez Coll, Juan Carlos (2001): "Las deciones individuales" en La Economía de Mercado, virtudes e inconvientes
Zafirovski, Milan (2003): "Human Rational Behavior and Economic Rationality" in Electronic Journal of Sociology (2003)
--- (December 2, 199): "The human factor: rational economic man" in The Economist (US)
If you read Spanish, a wonderful site for explanations of economics of all sorts is at the University of Malaga en Spain: http://eumed.net/cursecon/.