A legal mechanism to protect a person who relies to their detriment upon an assumption or expectation created by another person. It must be unconscionable for the other person not to be held accountable for that detriment. An example is estoppel by representation where a person relies upon the representation of another to their detriment and, the detriment is caused by reliance on the representation, the person who made the representation is estopped from denying that they made that representation.