The promise principle and its roots in a certain type of morality of individual obligation, which play the central role in Charles Fried’s vision of Contract law, have importantly contributed to rescuing Contract law from absorption into Tort law and from the imposition of externally imposed standards that are collective in origin. It makes a mammoth contribution to alerting us to the tyranny of interference with individual self-determination. However, this essay questions whether a promise centered system derived from a moral philosophy of promising (without an observable and testable foundation in reality) and geared to internal individual obligation and duty can provide the basis on which the public law can decide the hard cases in contract law. First, the promise-sufficient principle won’t help when the promises are incomplete. Second, this essay hypothesizes that there is an evolutionary trend toward efficient social contracts (or institutions of any kind), and therefore, if different communities at different times, using the latitude that our cultural genetic make up allow, choose to veer away from that trend, they will suffer by comparison with communities that do not. It is as if they are competing. In understanding what contract law should look like normatively, we must move beyond the purported internally reflective, a priori processes of individual will and understand, through casual and formal empirics and comparisons among economies, the background of how parties’ externally expressed natural impulses act to coordinate on social problems in the games of life. The law should look to how parties act to coordinate through exchange and produce improving welfare when they construct contracts and the rules of contractual enforcement. In that way, contract law will develop around, and not in a manner at odds with, naturalistic sources for normative principles, ones that are consonant with the parties’ own expressions.


contract interpretation, promise principle, morality, Charles Fried, Contract as Promise, self-imposed obligation, utility, external standards, autonomy, naturalistic, neuroscience, welfare improvement, efficient equilibrium, human nature, Immanuel Kant, David Hume, Kenneth Binmore, instrumentalism

Publication Date


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Place of Original Publication

Suffolk University Law Review

Publication Information

45 Suffolk University Law Review 843 (2012)

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Contracts Commons


COinS Juliet P. Kostritsky Faculty Bio