Who can object to the libertarian principles of individual freedom, personal responsibility, and the right to hold property—at least in the abstract? The problem is that the real world is never "abstract."

All philosophies must ultimately confront reality, and the more radical versions of libertarianism (there are many, from extreme anarchism to limited government "minarchism") rely on terminally deficient models of human nature and society. Let's (very briefly) take a look at the problem.

The libertarian model of individual psychology is grounded in the utilitarian, neo-classical economics model of "Homo economicus" (economic man). Our motivations can be reduced to the single-minded pursuit of our (mostly material) self-interests. Accordingly, mainstream economists seem to consider it their mission in life to help us do so more "efficiently." The Nobel economist Amartya Sen many years ago scathingly characterized this simplistic model as "rational fools who are decked out in their one, all-purpose preference function."

The selfish-actor model of human nature was tacitly endorsed with the rise of "Neo-Darwinism" in evolutionary biology during the 1970s, as epitomized in biologist Richard Dawkins' famous book The Selfish Gene. As Dawkins summed it up, "We are survival machines—robot vehicles blindly programmed to preserve the selfish molecules known as ... I shall argue that a predominant quality to be expected in a successful gene is ruthless selfishness ... we are born selfish."

A line from libertarian philosopher Robert Nozick's path-breaking book, Anarchy, State and Utopia, says it all: "Individuals have rights, and there are things no person or group [or state] may do to them without violating their rights." (When asked to specify what those rights are, libertarians often cite philosopher John Locke's mantra "life, liberty, and property.") Not to worry, though. Through the "magic" of Adam Smith's "invisible hand," the efficient pursuit of our self-interests in "free markets" will ensure the greatest good for the greatest number.

One problem with this (utopian) model is we now have overwhelming evidence that the individualistic, acquisitive, selfish-gene model of human nature is seriously deficient; it is simplistic, one-sided, and in reality, resembles the pathological extremes among the traits that we find in our society. The evidence about human evolution indicates that our species evolved in small, close-knit social groups in which and sharing overrode our individual, competitive self-interests for the sake of the common good. (This scenario is reviewed in my books The Fair Society and Holistic Darwinism.) We evolved as intensely interdependent social animals, and our sense of toward others, our sensitivity to reciprocity, our desire for inclusion and our loyalty to the groups we bond with, the intrinsic satisfaction we derive from cooperative activities, and our concern for having the respect and approval of others all evolved in humankind to temper and constrain our individualistic, selfish impulses (as Darwin himself pointed out in The Descent of Man).

So we are not, after all, like bumper cars in a carnival, where we all range freely, and, if we cause "harm" by crashing into others, we simply say "excuse me" and move on.

Rather, we are (most of us) embedded in an exceedingly complex network of social relationships, many of which are vital to our well-being. Every day, we confront issues relating to the needs and wants of others and must continually make accommodations. And in addressing these conflicting interests, the operative norm is, or should be, fairness, a balancing of the interests and needs of other parties, other "stakeholders."

Indeed, libertarians generally have no model of society as an interdependent group with a common purpose and common interests. For instance, the canonized conservative economist Friedrich Hayek posited a stark choice between two alternative models—either a "free market" of atomized individuals rationally pursuing their self-interests in transactional relationships or an authoritarian, coercive "state" that seeks control over us. In Hayek's words, "socialism means slavery."

The libertarian novelist Ayn Rand went even further. As she saw it, there is a perpetual class war going on between the "creators" and "producers," on the one hand, and the great mass of "parasites" and "moochers" who use government to steal whatever they can from the deserving few. One of Rand's heroes, the defiant architect Howard Roark in her novel The Fountainhead, tells us: "All that proceeds from man's independent ego is good. All that which proceeds from man's dependence upon men is evil ... The egotist in the absolute sense is not the man who sacrifices for others ... Man's first duty is to himself ... His moral law is to do what he wishes, provided his wish does not depend primarily upon other men ... The only good which men can do to one another and the only statement of their proper relationship is 'hands off!'"

The benign free-market model of society is equally deficient. Many libertarians seem to be myopic about the prevalence of self-interested "organizations" in the marketplace, from the many millions of mom-and-pop businesses with only a few employees to mega-corporations with hundreds of thousands of workers (whose freedom they may severely restrict). These "corporate interests" sometimes oppose the common interest and perpetrate malfeasance. (Do we need to rehearse the recent examples of Enron, Capital , Countrywide, Goldman Sachs, BP, Massey Energy, and other disasters?) So-called free markets are routinely distorted by the wealthy and powerful, and the libertarians' crusade for lower taxes, less regulation, and less government plays into their hands. Perhaps unwittingly, anti-government libertarians would have us trade democratic self-government for an oligarchy.

A more serious concern is that the libertarian fixation with individual freedom distracts us from the underlying biological purpose of a society. The basic, continuing, inescapable problem for humankind, as for all other living organisms, is biological survival and reproduction. Whether we are conscious of it or not, most of us spend a large majority of our time and energy engaged in activities that are directly or indirectly related to meeting no fewer than 14 domains of "basic needs"—biological imperatives ranging from such commonplace things as food, clothing, and shelter to physical and mental health and the reproduction and nurturance of the next generation.

In a very real sense, therefore, every organized economy and society represents a "collective survival enterprise"—an immensely complex "combination of labor" (a term I prefer to the traditional "division of labor") upon which all of our lives literally depend. And our first collective obligation is to ensure that all of our basic needs are met. If there is a "right to life," as our Declaration of Independence and pro-life conservatives aver, it does not end at birth; it extends throughout our lives, and it imposes on all of us a responsibility for ensuring the "no-fault" needs of others when they cannot for various reasons provide for themselves.

So why is libertarianism unfair? It rejects any responsibility for our mutual right to life, where we are all created approximately equal. It would put freedom and property rights ahead of our basic needs, rather than the other way around. It is also oblivious to the claims for reciprocity, an obligation to contribute a fair share to support the collective survival enterprise in return for the benefits that each of us receives. And it is weak on the subject of equity (or social merit) as a criterion for respecting property rights. It presumes a priori that property holdings are deserved, rather than making merit a precondition. Imposing a test of merit would put strict limits on property rights. Finally, it is anti-democratic in that it rejects the power of the majority to restrain our freedom and limit our property rights in the common interest, or for the general welfare.

The conservative Washington Post op-ed writer Michael Gerson observed in a recent column that "Conservatives hold a strong preference for individual freedom. But they traditionally have recognized a limited role for government in smoothing the rough edges of a free society. This concern for the general welfare helps minimize the potential for revolutionary change while honoring a shared moral commitment to the vulnerable." This kind of "traditional" Burkean (and Platonic) conservativism is radically opposed to libertarianism, which Gerson calls a teenage that we need to outgrow. Freedom, as the social commentator Charles Morgan put it many years ago, is the space created by the surrounding walls. It's time to begin paying to the walls.