Promises are one of the bases of morals and ethics and also of human society: Very much of human interaction is only possible on the basis of agreements about supposed facts and values and about promises and contracts.

The basic moral rules about promises seem to be that

• one should only make such promises as one knows one can probably keep;
• one should keep one's promises; and
• one should explain as soon as possible if and why one cannot keep a promise to those one made the promise to.

Note that these norms are all related to the making and keeping of agreements, not only about what  facts and values are, but also how to retain or alter them,  and making one's own behavior reliable and predictable and understandable for others, all of which are involved in human cooperation.