Levine and colleagues engage morality primarily through the lenses of game theory and research on morality that focuses on utilitarian and deontological reasoning. Their contractualist model is well reasoned from these perspectives but misses opportunities to incorporate insights from other relevant literatures. We contend that the interdependent choices explained by their model primarily involve questions of justice/fairness rather than morality more broadly. Many perspectives differentiate between justice and morality (e.g., Graham et al., Reference Graham, Haidt, Koleva, Motyl, Iyer, Wojcik and Ditto2013; Skitka, Bauman, & Mullen, Reference Skitka, Bauman, Mullen, Hegtvedt and Clay-Warner2008), and the justice and morality literatures developed separately and remain largely distinct (Skitka, Bauman, & Mullen, Reference Skitka, Bauman, Mullen, Sabbagh and Schmitt2016). Much of the justice literature focuses on the fairness of interpersonal interactions; thus, it is important to consider theories of justice. Moreover, research on negotiations incorporates aspects of game theory but also highlights psychological processes that can complicate interpersonal agreement. Below, we connect the contractualist model to the vast justice literature and negotiation research, which support some parts of the model while challenging others.

The justice literature comprises work primarily in psychology and organizational behavior that examines how people evaluate fairness and deservingness in interpersonal interactions (see Greenberg & Colquitt, Reference Greenberg and Colquitt2005). People care about the fairness of outcomes (distributive justice), procedures (procedural justice), and interpersonal treatment (interactional justice) in their interactions with others. Distributive and procedural justice closely parallel the notions of “welfare-based” and “action-based” standards, respectively. Levine et al. cite equity theory (Adams, Reference Adams1965), but other justice research describes additional distributive schemes people deem appropriate depending on the context and relations among those involved (e.g., equity, equality, need; Deutsch, Reference Deutsch1975). Moreover, decades of research examines criteria for fair procedures (e.g., free from bias, applied consistently, accurate, correctable, and provide voice; Leventhal, Reference Leventhal, Gergen, Greenberg and White1980). Distributive and procedural justice rules influence people’s negotiation behavior and contribute to the “abstractions” in model-based or model-free agreements in the contractualist model.

The contractualist model insufficiently considers the role of procedures in determining fair outcomes. Fair procedures often prompt people to accept outcomes they otherwise would reject (i.e., the fair process effect; Lind & Tyler, Reference Lind and Tyler1988); this research suggests welfare-based and action-based standards may interact. In short, the contractualist model overlooks robust evidence that people’s perceptions of outcomes depend on the process, not just the value they would receive relative to alternative agreements (Hollander-Blumoff & Tyler, Reference Hollander-Blumoff and Tyler2008).

Given the existence of multiple justice rules, determining which justice rule to apply in a given situation and reaching consensus among parties regarding which rule is optimal is challenging for several reasons. First, people’s fairness judgments depend on their self-interest, relational motives, moral convictions and values, and other situational elements (Skitka, Bauman, & Lytle, Reference Skitka, Bauman, Mullen, Hegtvedt and Clay-Warner2008; see also Fiske, Reference Fiske1992). The contractualist model insufficiently accounts for how competing justice principles could apply in a situation. Second, egocentrism – the tendency to perceive situations from one’s own perspective – influences fairness perceptions (Burrus & Mattern, Reference Burrus and Mattern2010; van Prooijen, Reference van Prooijen, Hegtvedt and Clay-Warner2008) and complicates “ad hoc negotiation” and “mental simulation” in the contractualist model. Negotiators overestimate the strength of their arguments, the fairness of their positions, and how much others will agree with them (Neale & Bazerman, Reference Neale and Bazerman1985; Thompson & Loewenstein, Reference Thompson and Loewenstein1992). Moreover, egocentrism limits parties’ understanding of others’ perspectives even after negotiating (Chambers & DeDreu, Reference Chambers and De Dreu2014). Naive realism—the tendency to perceive oneself as rational and objective and expect others to share one’s perspective—exacerbates egocentrism and inhibits reaching negotiated agreements (Chambers & DeDreu, Reference Chambers and De Dreu2014). Although Levine et al. mention people’s “false beliefs” about others’ mental states, their model does not explain how these false beliefs systematically distort bargaining and hinder agreement. Moreover, the influence of egocentrism on mental simulations may lead to proposals likely to be rejected by the other party, prompting people to re-evaluate their conclusions or engage in ad hoc negotiation. Thus, egocentrism limits people’s abilities to accurately mentally simulate fair agreements, and incorporating this research into the contractualist model may enhance its scope regarding predictors of moral flexibility.

Finally, justice research also sheds light on how people make and use fairness judgments. Fairness heuristic theory, along with related work on the uncertainty management model, provide a foundation for the contractualist model by explaining when and how people use mental shortcuts when making fairness judgments under uncertainty (Lind, Reference Lind, Greenberg and Cropanzano2001; Van den Bos & Lind, Reference van den Bos, Lind and Zanna2002). For example, people use information about procedural fairness as a heuristic when outcome fairness is unclear. Moreover, fairness judgments, once formed, guide subsequent judgments about related situations until a shock prompts reassessment. For example, people may trust decision-makers and perceive them to be fair, until an immoral outcome prompts them to re-evaluate the fairness of the procedures (Mullen & Skitka, Reference Mullen and Skitka2006) or the agent (Skitka et al., Reference Skitka, Bauman and Lytle2009). Thus, justice research provides considerable insight into the moral flexibility component of the contractualist model.

In conclusion, Levine and colleagues have broadened our understanding of how people make moral (or fairness) judgments under some circumstances, but that understanding would be further enhanced by incorporating research on justice, egocentrism, and negotiations. Moreover, doing so may help to broaden the model’s scope as any comprehensive theory of moral cognition would need to address not just what people would agree to based on the quality of their alternatives (i.e., their bargaining power), but also whether existing resource distributions and power hierarchies are just. A comprehensive theory of moral cognition would also need to be able to account for morality beyond transactions and justice considerations, including purity and loyalty concerns. Having a restricted scope does not negate the potential value of what the model can explain, but similar limitations in scope prompted researchers to look for more comprehensive alternatives in the past (e.g., Shweder & Haidt, Reference Shweder and Haidt1993). Returning to Parfit’s (Reference Parfit2011) mountaineering analogy and advice that the surest way forward for each moral theory is to discover its paths of convergence with others, we hope to have demonstrated the convergence between justice theories and resource-rational contractualism as well as some challenges to reaching the summit via the contractualist path.