The traditional rule in contract law is that a promise to discharge a debt must be supported by consideration. In this case, Henry's promise not to complain does not constitute sufficient consideration to discharge the debt. Consideration must have some economic value and be capable of being expressed in tangible terms. Since Henry had no legal right to complain about his disinheritance, his promise to refrain from doing so holds no tangible value. The leading case, White v Bluett (1853), supports this position, where it was held that a son's promise to stop complaining was not valid consideration to discharge a debt because the son had no legal right to complain about his father's will. 

Key Point: Consideration in contract law must be something of tangible value exchanged between parties. A promise based on refraining from an action that one has no legal right to undertake does not constitute valid consideration, ensuring that agreements are based on actual economic exchanges.