The author accentuates that the promise would otherwise be unenforceable for lack of consideration. It thus hinders a party, from revoking a promise he/ she made to another, who reasonably relied on it.
The invocation of promissory estoppel relies on three major elements. To start with, if a party by his words or conduct, makes a promise, which he reasonably expected to induce action or forbearance of substantial character on the part of the promise. with the intention of creating a legal relationship, the doctrine holds as was in the case of Central London Properties Ltd. Vs. High Trees House Ltd.,  K.B. 130. Secondly, the doctrine holds, if the promisee reasonably relies on the promise. This means that the promise did in fact, induce action or forbearance, as was held in the case of Hoffman Vs. Red Owl Stores, Inc. 26 Wis.2d 683, 133 N.W.2d 267 (1965). It also holds if, from action or forbearance, promisee suffered economic loss. However, the detrimental loss suffered is not a necessity, as in the case of Alan &. Co vs. El Nasr (1972), and as such, a plaintiff or the promise, ought to prove that upon reliance on the promise, his position changed.
Most importantly, from its origin, “waiver,” the doctrine of promissory estoppel is regarded as an equitable doctrine. As such, it must be evidently inequitable, for a promissory to go back on a promise he/ she made, before applying the doctrine. In effect, this element covers certain contexts, in which promisee takes advantage of the promissory, by extracting a promise as was held in the case of D &. C Builders vs. Rees (1966). In such cases, the judge must evaluate whether it is just to enforce the promise. A promise may be limited by time. In regards to this, promissory estoppel as opposed to a contract modification, supported by consideration, is not of permanent effect. As was .held in the case of High Trees, where the promise last only during the world war.