 The consideration doctrine presents a challenge for the contract-as-promise theory because the rules of promissory morality do not limit obligations in any analogous way. Other limits on contract law’s willingness to enforce promises—for instance, doctrines relating to fraud and duress— might track analogous limits in the morality of promising. But there is no obvious reason to suppose that a gratuitous promise—to collect a friend from the airport, to give a child a coveted treat, or to keep a friend’s secret—cannot generate moral obligations. The challenge is bolstered by the fact that the consideration requirement remains entrenched in the common law of contracts despite repeated academic criticism. Even civil law, which includes no formal analog to consideration, nevertheless favors legal enforcement of exchange promises in a number of ways.