 Contract law egalitarianism draws support from an extensive literature in moral and political philosophy that has questioned the legitimacy of exchange relations in unequal societies. John Rawls’ seminal work has been especially influential. Rawls (2005: 266–267) observes that the free market allows everyone to gain through private exchange, but it also allows those who are already more advantaged to capture as much of the contractual surplus as they are able to, so that “the invisible hand guides things in the wrong direction … maintaining unjustified inequalities and restrictions on fair opportunity.”   Contract and property law, together with institutions of tax-and-transfer, arguably fall within the “basic structure” of society—that is, the category of institutions that so pervasively influence people’s lives as to demand special justification (Murphy 1998: 260–261). For Rawls, the basic structure’s justification depends on what parties would rationally agree to ignorant of various aspects of their situation, including their economic circumstances. Rawlsian “maximin principles” prioritize the interests of those who are worse off. While a full analysis of Rawls’ work and its influence on modern contract theory is beyond the scope of this entry, readers can see related entries (on  distributive justice  and the  original position)  for more detail.  Rawlsians are hardly alone in questioning the legitimacy of private exchange in circumstances of inequality. Marx (Das Kapital, 3:339–40) famously questions the alleged “natural justice” of private exchange and the juristic treatment of economic transactions “as willful acts of the parties concerned”, viewing exchange relations in capitalist societies as invariably exploitative (see discussion in Arneson 1981: 205; cf. Cohen 1995). Exploitation raises questions of meaningful consent and coercion, some of which were discussed earlier (see  §2.2).  But implicit in Marx’s concept of exploitation (assuming the view to be less than fully skeptical of considerations of justice) is a distinct moral notion: the failure of private exchange to ensure parties receive as much as they deserve based on their productive contributions and sacrifices (cf. Cohen 1995: 116–117; on moral desert, see below).  Contract law egalitarianism at the institutional level confronts two standard criticisms. First, it is not obvious that judges have the authority or competence to promote distributive justice. A tax-and-benefit scheme may be a more effective means of promoting the interests of the economically worse off than private law, though whether this is true remains an open empirical question (Kaplow &amp; Shavell 1994; Lucy 2007: 352–6; Liscow 2021 [Other Internet Resources]). Second, contract disputes are private affairs, and people deserve protection from being singled out to bear the burdens associated with the collective’s moral responsibilities. Thomas Nagel (1991: ch9) describes a division of moral labor between, on the one hand, institutional actors responsible for the basic legal structure, and, on the other, ordinary citizens acting in their private capacity. In general, persons may lead better lives if freed from the obligation to manage their exchange relations altruistically. The point seems consistent, however, with courts being obliged to enforce negative duties—for instance, a duty not to take advantage of the collective’s failure to secure distributive justice (Murphy 1998: 266; Bagchi 2014). The common law’s unconscionability doctrine appears tailor-made to police this kind of predation by the economically privileged of the disadvantaged.  We turn from the institutional-level question to the question of what contracting parties individually owe one another. Contracts generate surplus from cooperation—each side typically stands to benefit through exchange. How that surplus ought to be divided is not necessarily settled by assuming that the parties transact from a place of equality. Robert Nozick’s (1974) famous discussion of “justice in transfer” provides a convenient starting point for exploring the ethics of surplus sharing. Nozick suggests that inequalities arising out of voluntary transactions do not give rise to a question of justice, given fair background conditions. On Nozick’s “voluntarist” view, whatever sharing scheme is voluntarily agreed to (setting aside stealing, fraud, etc.) is just, or, alternatively, no question of justice is raised by a division the parties consented to (for a more detailed statement, see Nozick 1974: 149–182). There are other more qualified strains of voluntarism. A “sufficientarian” might insist that the consented-to division must satisfy a minimal baseline. Sterba (1986: 8) articulates a “Needs and Agreement Principle” under which the results of voluntary agreement and private appropriation are morally justified only insofar as each person is guaranteed the goods necessary to meet the normal costs of satisfying her basic needs. Sufficientarian constraints might entail, for example, that those involved in the provision of essential goods or services—basic medicine or education—owe more robust duties to those with whom they contract.  Moving further away from pure voluntarism, a prominent approach distinguishes between deserved and undeserved shares of cooperative surplus. Nozick is sometimes criticized for assuming that persons are entitled to that portion of the market price for their goods and services characterizable as “scarcity rent” (B. Fried 1995: 230). Rent is defined as a gain that exceeds what is necessary to incentivize cooperative exchange. Excess gains in market exchange are often attributable to natural scarcity, including scarcity of natural talents. Whether persons deserve such windfalls flowing from brute luck in the birth lottery remains a deeply contested moral question. Some find a desert-basis in effort and other forms of personal sacrifice, including delayed gratification (as in investment contracts). On this view, parties are owed at least as much of the surplus from a cooperative scheme as would constitute fair compensation for their sacrifices (Reiman 1983; Sadurski 1985; Milne 1986). Others finds a desert-basis in productive contribution. Parties to contractual exchange deserve fair remuneration for their marginal product (D. Miller 1976; Miller 1999; J. Riley 1989). Marginal product is defined as a factor’s distinctive contribution to raising the value of goods and services, holding other factors constant. The central moral intuition, here, is that people ought to receive benefits from exchange in proportion to how much they improve the wellbeing of others (Lamont 1994). The productive contribution theory is sometimes motivated on general consequentialist grounds (rather than notions of moral desert), with rents explained as the premium necessary for incentivizing parties to put their talents to productive and wellbeing-maximizing use (Arnold 1987).  Both the effort and productive contribution theories rely on concepts that invite further specification. Consider the concept of marginal product. What is produced by one’s efforts depends on the productivity of the tools and raw materials one has at one’s disposal. The state is a contributing participant, also, in every cooperative exchange (B. Fried 1995). Given that many people make interdependent contributions to social product, the link between any individual’s labor and output seems too attenuated to ground anything more determinate than the claim that people deserve something based on what they produce (Scanlon 2018: ch8). And it is hard to see how so general a normative claim could bear the weight of justifying any precise proposal for surplus division.  Gauthier (1986: 140–141, 152–153) suggests that cooperative surplus might be split according to the ratio of the parties’ “individual relative benefit from cooperation”. Each party’s relative benefit from exchange is measured by their next best option. If A and B generate $10 of cooperative surplus, and A could have earned $3 acting independently of B, while B could have earned $4, then the maximum A can claim of the surplus is $6 consistent with inducing B’s willing cooperation, and the maximum B can claim is $7 for a parallel reason. When the $10 surplus is split based on a 6:7 ratio, each party receives such benefits as she would expect apart from cooperation and, in addition, receives a share of the surplus proportionate to her potential for benefiting from the exchange. Gauthier defends the proposal as a solution to a bargaining problem confronting self-interested rational agents, but it is morally contestable. It remains unclear why a party should receive more just because they had a better alternative, since the availability of an attractive alternative may be a function of brute luck. Moreover, Gauthier’s principle does not guarantee that parties receive a share commensurate to sacrifice or productive contribution (Van Parijs 1996).  The proposals considered so far invoke considerations of pre-institutional morality and/or rationality. But the ethics of surplus sharing might instead be traced to established customs. Macneil (1986) suggests that markets give rise to complex norms of “gift-giving” in commercial exchange. These gift-giving norms encourage agents to refrain from claiming as much of the surplus as possible and have an important role to play in maintaining social bonds, especially in contexts where constant haggling undermines trust and creates impediments to contracting. For example, sellers of antiques will offer discounts to those who reveal their enthusiastic interest in purchasing an item. By rewarding disclosures against self-interest, the sellers promote solidarity and cooperation in the market for antiques. Macneil observes that norms of gift-giving are more likely to emerge where the cooperative surplus is large and repeat interaction generates high interdependence.  A question facing the social solidarity view is why market participants should feel obliged to comply with customary norms. Custom is sometimes portrayed “as the embodiment of what parties in the relevant community actually, not fictitiously, consent to when they manifest their intention to be legally bound” (Barnett 1992: 1192).   On this view, the parties’ expectations become the grounds for complying with the relevant surplus sharing norms, although expectations, even ones based on longstanding customs, are not always reasonable or fair. Another possibility is that the reasons for compliance may be grounded in general, consequentialist considerations concerning the importance of reinforcing socially beneficial customs. A third is that compliance produces additional surplus by lowering transaction costs.  In the final analysis, a broad range of distributive considerations arguably ought to shape bargaining behavior, and the above discussion is not intended to be exhaustive. As should be apparent from the lack of convergence among theorists, the moral question of justice in transfer that is at the heart of contract remains far from settled. 