Implicit exceptions bring about a third type of value system called a formal value system. Whether idealized or realized, this type contains an implicit exception associated with each value: "as long as no higher-priority value is violated". For instance, a person might feel that lying is wrong. Since preserving a life is probably more highly valued than adhering to the principle that lying is wrong, lying to save someone’s life is acceptable. Perhaps too simplistic in practice, such a hierarchical structure may warrant explicit exceptions.