In addition to the human law, dictated by reason, man also has the divine law, which, according to Question 91, is dictated through revelation, that man may be "directed how to perform his proper acts in view of his last end", "that man may know without any doubt what he ought to do and what he ought to avoid", because "human law could not sufficiently curb and direct interior acts", and since "human law cannot punish or forbid all evil deeds: since while aiming at doing away with all evils, it would do away with many good things, and would hinder the advance of the common good, which is necessary for human intercourse." Human law is not all-powerful; it cannot govern a man's conscience, nor prohibit all vices, nor can it force all men to act according to its letter, rather than its spirit.