Promissory estoppel was first articulated as a distinct basis of liability in §90 of the First Restatement. The original formulation, with subtle revisions, survives in §90 of Restatement, Second. Although the Restatement section does not itself call the doctrine promissory estoppel, this name is firmly established by long usage.
Several factors must be considered in deciding whether promissory estoppel relief is appropriate, as will be discussed shortly. However, its essential elements can be stated simply: A promise coupled with detrimental reliance on that promise. Although these two prerequisites do not always receive the same emphasis, a combination of them must be present for relief to be granted.