The value of a promise

The question “What makes a promise binding?” has received much attention both from philosophers and lawyers. One argument is that promises are binding because the act of making a promise creates expectations in the promisee, which expectations it would be morally wrong to disappoint. Another argument is grounded in the effects engendered by the making of a promise, specifically actions taken in reliance upon the promise. These two positions, the so-called expectation and reliance theories, have traditionally been thought to be incommensurable. In a recent article, ‘Promises and Practices’, Thomas Scanlon advances a theory of promising developed out of both of these positions. This article argues that Scanlon's argument fails because it cannot avoid the incommensurability of the expectation and reliance principles.