Introduction: promise as a type of obligation

A promise is considered as a type of obligation, both in morality and law, but what does it mean to call promise an obligation? Having explored that question at the beginning of this chapter, the source of the obligatory nature of promise will be considered. The focus of the study of that second question will, in this chapter, be on promise within morally obligatory systems; the question of the binding force of an obligation in legal systems is largely considered in the next chapter. However, the question of the moral and legal force of an obligation such as promise cannot be wholly separated, as many theories of law and morality see the two systems as inextricably linked. Thus, a dominant theory of law posits that the force of contract derives from the fact that a contract is a promise, and that contracts should therefore be kept because promises should be kept. Such a theory evidently necessitates that one asks why promises ought to be kept. That fundamental, and essentially moral, question requires an exploration of the various theories concerning why promises ought to be kept, an exploration of which comprises the bulk of the discussion in this chapter.