Justification to other people › Assurances and the importance of a promise

Scanlon's chapter on promises develops an account centered on assurance. His Principle F describes conditions involving intentionally creating an expectation, the other's desire for assurance, the aim of giving that assurance, and the parties' knowledge of the relevant intentions and beliefs. Under its conditions, and absent special justification, performance is required unless the recipient consents to release.

The detailed conditions show why predicting an action and promising it differ. Saying that you expect to visit on Friday can give someone information without necessarily undertaking a commitment to seek their release before changing plans. A promise supplies a different kind of assurance. An account that treated every voluntarily created expectation as equally binding would restrict ordinary communication too severely.

Return to the lift. If you offered it precisely so that your friend could stop worrying about transport, your assurance has given them something they wanted. The moral reason is not limited to the money or minutes eventually lost if you cancel. The ability to settle a practical question through another person's undertaking is itself part of the issue.

This does not make promises absolute. The account includes the possibility of special justification and release. But “I now prefer something else” is not automatically such a justification. The difference between an assurance and an unenforced intention explains why changing a preference does not simply erase a commitment.

The example also shows why contractualism should not be presented as hostile to duties. It offers an account of how particular duties can be justified. Disagreement with another theory may concern the explanation of the duty rather than whether a duty exists at all.