Aquinas divided law into four categories, namely eternal law, natural law, human law and divine law. Eternal law is God's reason, applies to the entire universe, and is the origin of all laws. Eternal law is the highest law and the source of all laws. Natural law and human law must obey eternal law. Natural law is the law that governs human behavior. It is the embodiment of God's reason in human reason and applies to all human beings. Human law is the law promulgated by the ruler, including the law of peoples and civil law. It is a special application of natural law. Human law must be guided by divine law. Divine law, that is, canon law, the law given to mankind by God.