It seems that fairness is an idea whose time has come. True, some cynics view fairness as nothing more than a mask for self-interest. But the cynics are wrong. One of the important findings of the emerging, multi-disciplinary science of human nature is that humans do, indeed, have an innate sense of fairness. We regularly display a concern for others' interests as well as our own, and we even show a willingness to punish perceived acts of unfairness. The accumulating scientific evidence for this distinctive human trait, which is reviewed in my new book, suggests that it has played an important role in our evolution. It has served to facilitate and lubricate the close-knit social organization that has been a key to our success as a species. Among other things, the evidence for this trait includes anthropologist Donald Brown's finding, reported in his landmark study, Human Universals, that altruism, reciprocity, and a concern for fairness are cultural universals. Likewise, in the field of behavior genetics, many studies have documented that there is a genetic basis for traits that are strongly associated with fairness, including altruism, empathy and "nurturance." In the brain sciences, the experiments of Joshua Greene and his colleagues have identified specific brain areas associated with making moral choices. Another team, headed by Alan Sanfey, pinpointed a brain area specifically associated with feelings of fairness and unfairness when subjects were participating in the so-called "ultimatum game" in his laboratory. There is also the extensive research by evolutionary psychologists Leda Cosmedes and John Tooby and a number of their colleagues on what they term "social exchange" (or reciprocity) - which they point out exists in every culture. Cosmedes and Tooby have concluded that humans possess a discreet "mental module" -- a dedicated neurocognitive system - for reciprocity behaviors. In a similar vein, the work on "strong reciprocity theory" in experimental and behavioral economics has repeatedly demonstrated that even altruistic behaviors can be elicited in cooperative situations if there is a combination of strict reciprocity and punishment for defectors. Finally, it has been shown that even some nonhuman primates display in a rudimentary form some of the traits associated with fairness behaviors in humans. For instance, primatologist Frans de Waal, in a classic laboratory experiment, clearly demonstrated the existence of reciprocity behaviors in capuchin monkeys. It seems evident that a sense of fairness is an inborn human trait. It means, quite simply, that we are inclined to take into account and accommodate to the needs and interests of others. However, it is equally clear that our sense of fairness is labile. It can be subverted by various cultural, economic and political influences, not to mention the lure of our self-interests. And, of course, there are always the "outliers" - the Bernie Madoffs. In fact, our predisposition toward fairness, like every other biological trait, is subject to significant individual variation. Numerous studies have indicated that some 25-30 percent of us are more or less "fairness challenged." Some of us are so self-absorbed and egocentric that we are totally insensitive and even hostile to the needs of others. Ebenezer Scrooge in Charles Dickens's "A Christmas Carol," and the banker Henry F. Potter in Frank Capra's timeless Christmas movie "It's a Wonderful Life" were caricatures, of course, but many of us have seen likenesses in real life. Thus fairness is not a given. It's an end that can only be approximated with consistent effort and often in the face of strong opposition. And in the many cases where there are conflicting fairness claims, compromise is the indispensable solvent for achieving a voluntary, consensual outcome. At the individual level, fairness is an issue in all of our personal relationships -- in our families, with our loved ones, with friends, and in the workplace. We are confronted almost every day with concerns about providing, or doing, a "fair share," reciprocating for some kindness, recognizing the rights of other persons, being fairly acknowledged and rewarded for our efforts, and much more. However, fairness is also an important, "macro-level" issue in our society, and the debate about what is often referred to as "social justice" can be traced back at least to Plato's great dialogue, The Republic. For Plato, social justice consists of "giving every man his due" (and every woman, of course). His great student, Aristotle, characterized it as "proportionate equality." Plato also advanced the idea that every society entails a social "compact" - a tacit understanding about the rights and duties, and benefits and costs, of citizenship - and he viewed social justice as the key to achieving a stable and harmonious society. The idea that there is a more or less explicit "social contract" in every society is more commonly associated with the so-called social contract theorists of the seventeenth and eighteenth centuries - such as Rousseau, Hobbes, and Locke - and more recently, John Rawls. Rousseau fantasized about free individuals voluntarily forming communities in which everyone was equal and all were subject to the "general will." Thomas Hobbes, in contrast, envisioned a natural state of anarchic violence and proposed, for the sake of mutual self-preservation, that everyone should be subject to the absolute "sovereign" authority of the state. John Locke, on the other hand, rejected this dark Hobbesian vision. He conjured instead a benign state of nature in which free individuals voluntarily formed a limited contract for their mutual advantage but retained various residual rights. The philosopher David Hume, and many others since, have made a hash of this line of reasoning. In a devastating critique, A Treatise of Human Nature (published in 1739-40), Hume rejected the claim that some deep property of the natural world (natural laws), or some aspect of our past history, could be used to justify moral precepts. Among other things, Hume pointed out that even if the origins of human societies actually conformed to such hypothetical motivations and scenarios (which we now know they did not), we have no logical obligation to accept an outdated social contract that was entered into by some remote ancestor. With the demise of the natural law argument, social contract theory has generally fallen into disfavor among philosophers, with the important exception of the work of John Rawls. In his 1971 book, A Theory of Justice, Rawls' formulation provoked a widespread reconsideration of what constitutes fairness and social justice and, equally important, what precepts would produce a just society. Rawls proposed two complementary principles: (1) equality in the enjoyment of freedom (a concept fraught with complications), and (2) affirmative action, in effect, for "the least advantaged" among us. This would be achieved by ensuring that the poor have equal opportunities and that they would receive a relatively larger share of any new wealth whenever the economic pie grows larger. Although Rawls' work has been exhaustively debated by philosophers and others over the years, it seems to have had no discernable effect outside of academia. However, there is one other major exception to the general decline of social contract theory that is perhaps more significant. Over the past two decades, a number of behavioral economists, game theorists, evolutionary psychologists and others have breathed new life into this venerable idea with a combination of rigorous, mathematically-based game theory models and empirical research. Especially important is the work of the mathematician-turned-economist Ken Binmore, who has sought to use game theory as a tool for resuscitating social contract theory on a new footing. In his 2005 book, Natural Justice, Binmore describes his approach as a "scientific theory of justice," because it is based on an evolutionary/adaptive perspective, as well as the growing body of research in behavioral and experimental economics regarding our evolved sense of fairness plus some powerful insights from game theory. Briefly, Binmore defines a social contract in very broad terms as any stable "coordination" of social behavior - like our conventions about which side of the road we should drive on or pedestrian traffic patterns on sidewalks. Any sustained social interaction in what Binmore refers to as "the game of life" - say a marriage, a car pool, or a bowling league -- represents a tacit social contract if it is (1) stable, (2) efficient, and (3) fair. To achieve a stable social contract, Binmore argues, a social relationship should strive for an equilibrium condition - an approximation of a Nash equilibrium in game theory. The rewards or "payoffs" for each of the players should be optimized so that no one can improve on his or her own situation without exacting a destabilizing cost from the other cooperators. Ideally, then, a social contract is self-enforcing. As Binmore explains, it needs no social "glue" to hold it together because everyone is a willing participant and nobody has a better alternative. It is like a masonry arch that requires no mortar (a simile first used by Hume). The problem with this formulation - as Binmore recognizes -- is that it omits the radioactive core of the problem - how do you define fairness in substantive terms? As Binmore concedes, game theory "has no substantive content.It isn't our business to say what people ought to like." Binmore rejects the very notion that there can be any universals where fairness is concerned. "The idea of a need is particularly fuzzy," he tells us. In other words, Binmore's version of a social contract involves an idealization, much like Plato's republic, or free market (utopian) capitalism, or Karl Marx's utopian socialism. Fairness is whatever people say it is. I have taken a different approach. What I call a "biosocial contract" is distinctive in that it is grounded in our growing understanding of human nature and the basic purpose of a human society. It is focused on the content of fairness, and it encompasses a set of specific normative precepts. In the game theory paradigm, the social contract is all about harmonizing our personal interactions. Well and good. But in a biosocial contract, the players include all of the stakeholders in the political community and substantive fairness is the focus. A biosocial contract is about the rights and duties of all of the stakeholders in society, both among themselves and in relation to the "state". It is about defining what constitutes a "fair society." It is a normative theory, but it is built on an empirical foundation. I believe it is legitimate to do so in this case, because life itself has a built-in normative bias - a normative preference, so to speak. We share with all other living things the biological imperatives associated with survival and reproduction. If we do, after all, want to survive and reproduce - if this is our shared biological objective -- then certain principles of social intercourse follow as essential means to this end. First and foremost, a biosocial contract requires a major shift in our social values. The deep purpose of a human society is not, after all, about achieving growth, or wealth, or material affluence, or power, or social equality, or even about the pursuit of happiness. An organized society is quintessentially a "collective survival enterprise." Whatever may be our perceptions, aspirations, or illusions (or for that matter, whatever our station in life), the basic problem for any society is to provide for the survival and reproductive needs of its members. However, it is also important to recognize differences in merit and to reward them accordingly. Finally, there must also be reciprocity -- an unequivocal commitment on the part of all of the participants to help support the survival enterprise, for no society can long exist on a diet of altruism. Altruism is a means to a larger end, not an end in itself. It is the emotional and normative basis of our safety-net. As discussed at length in my book, a biosocial contract encompasses three distinct normative (and policy) precepts that must be bundled together and balanced in order to approximate the Platonic ideal of social justice. These precepts are as follows:  Goods and services must be distributed to each according to his or her basic needs (in this, there must be equality);  Surpluses beyond the provisioning of our basic needs must be distributed according to "merit" (there must also be equity);  In return, each of us is obligated to contribute to the collective survival enterprise proportionately in accordance with our ability (there must be reciprocity). The first of these precepts involves a collective obligation to provide for the common needs of all of our people. To borrow a term from the TV series Star Trek, this is our "prime directive." Although this precept may sound socialistic -- an echo of Karl Marx's famous dictum -- it is at once far more specific and more limited. It refers to the fourteen basic biological needs domains that are detailed in my book. Our basic needs are not a vague, open-ended abstraction, nor a matter of personal preference. They constitute a concrete but ultimately limited agenda, with measurable indicators for assessing outcomes. These fourteen basic needs domains include a number of obvious items, like adequate nutrition, fresh water, physical safety, physical and mental health, and waste elimination, as well as some items that we may take for granted like thermoregulation (which may entail many different technologies, from clothing to heating oil and air conditioning), adequate sleep (about one-third of our lives), mobility, and even healthy respiration, which can't always be assured. Perhaps least obvious but most important are the requisites for reproduction and the nurturance of the next generation. From this perspective, our basic needs cut a very broad swath through our economy and our society. The idea that there is a "social right" to the necessities of life is not as radical as it may sound. It is implicit in the Golden Rule, the great moral precept that is recognized by every major religion and culture. Furthermore, numerous public opinion surveys over the years have consistently shown that people are far more willing to provide support for the genuinely needy than the Scrooges among us would lead one to believe. (Some of these surveys are cited in my book.) Even more compelling, I believe, are the results of an extensive series of social experiments regarding distributive justice by political scientists Norman Frohlich and Joe Oppenheimer and their colleagues, as detailed in their 1992 book Choosing Justice. What Frohlich and Oppenheimer set out to test was whether or not ad hoc groups of "impartial" decision-makers behind a Rawlsian "veil of ignorance" about their own personal stakes would be able to reach a consensus on how to distribute the income of a hypothetical society. Frohlich and Oppenheimer found that the experimental groups consistently opted for striking a balance between maximizing income (providing incentives and rewards for "the fruits of one's labors," in the authors' words) and ensuring that there is an economic minimum for everyone (what they called a "floor constraint"). The overall results were stunning: 77.8 percent of the groups chose to assure a minimum income for basic needs. The results of these important experiments also lend strong support to the second of the three fairness precepts listed above concerning equity (or merit). How can we also be fair-minded about rewarding our many individual differences in talents, performance, and achievement. Merit, like the term fairness itself, has an elusive quality; it does not denote some absolute standard. It is relational, and context-specific, and subject to all manner of cultural norms and practices. But, in general, it implies that the rewards a person receives should be proportionate to his or her effort, or investment, or contribution. A crucial corollary of our first two precepts is that the collective survival enterprise has always been based on mutualism and reciprocity, with altruism being limited (typically) to special circumstances under a distinct moral claim -- what could be referred to as "no-fault needs." So, to close the loop, a third principle must be added to the biosocial contract, one that puts it squarely at odds with the utopian socialists, and perhaps even with some modern social democrats as well. In any voluntary contractual arrangement, there is always reciprocity -- obligations or costs as well as benefits. As I noted earlier, reciprocity is a deeply rooted part of our social psychology and an indispensable mechanism for balancing our relationships with one another. Without reciprocity, the first two fairness precepts might look like nothing more than a one-way scheme for redistributing wealth. As detailed in the book, a greater emphasis on reciprocity in American society would include such things as a more equitable tax code, higher taxes as necessary to support the basic needs of the 30 million (plus) Americans who suffer from extreme poverty, and a lifelong public service obligation beginning with a year of national service for everyone who is able to do so, or two years for those who receive special benefits like educational assistance. Some critics might object to such incursions on their freedom, but John Rawls' definition of fairness under a social contract provides a definitive rebuttal, in my view: "The main idea is that when a number of persons engage in a mutually advantageous cooperative venture according to rules, and thus restrict their liberty in ways necessary to yield advantages for all, those who have submitted to these restrictions have a right to a similar acquiescence on the part of those who have benefited from their submission." To conclude then, what the biosocial contract adds to Plato's great vision is the recognition that there are in fact three distinct categories, or types of substantive fairness and that these must be combined and balanced in appropriate ways. The substantive content of social justice consists of providing for the basic needs of the population, along with equitably rewarding merit and insisting on reciprocity. The biosocial contract paradigm also enlists the growing power of modern evolutionary biology and the human sciences to shed light on the matter, and it identifies an explicit set of criteria for reconciling (if not harmonizing) the competing claims that have been promoted by political ideologues of the Left and the Right. I believe that this framework offers our best hope for achieving and maintaining that elusive state of voluntary consent that is the key to a harmonious society - a Nash equilibrium writ large. This is an ideal worth striving for, because our own survival, and more certainly that of our descendants, may well depend upon it. As the great public park designer Frederick Law Olmstead put it, "The rights of posterity take precedence over the desires of the present." Nothing less than our evolutionary future is at stake.