After the Roman empire fell, the divine right of kings gave kings in Europe the right to rule. This theory of absolutism, which is based on Roman law, gives a sovereign individual absolute power without checks or balances.
Under this divine right of kings, monarchs claimed they received their right to rule directly from God. Though a monarch could not ignore lower laws, he had the power to overrule them. Having absolute power meant a king could unite cities and territories won through war or inherited, giving them a centralized form of government and expanding his power.
Though kings ruled by divine right, they largely left churches with spiritual authority. Many churches and religious leaders supported absolutism. By the 16th and 17th centuries, monarchs claimed to have absolute authority over all matters, including the church, and by the late 17th and early 18th centuries, kings continued to rule under this theory of divine right but no longer concerned themselves with matters of the church.
Several monarchs, including Frederick I of Prussia and Catherine the Great of Russia, used their absolute power to reform their kingdoms. They divided land equally among their subjects and allowed some free speech. Improving their kingdoms helped them justify their divine right. Near the end of the 18th century, the idea of a democratic government gained popularity, and many absolute rulers fell, including King Louis XVI and Queen Marie Antoinette of France.