• An illusory promise typically, by its terms, makes performance optional with the promisor. For example, if a guarantor promises to make good on the principal debtor’s obligation “as long as I think it’s in my commercial interest,” the promisor is not really bound. [Cases: Contracts 10(1). C.J.S. Contracts §§ 105–106, 108–113.]
illusory promise
A promise that appears on its face to be so insubstantial as to impose no obligation on the promisor; an expression cloaked in promissory terms but actually containing no commitment by the promisor.