Polybius believed that political change occurs naturally through either external conflicts or internal revolutions between different forms of government. He saw governments transitioning in a cycle from monarchy to tyranny to democracy and so on. To stabilize governments and slow this cycle, Polybius advocated for a mixed constitution that incorporated elements of different political principles, as seen in Sparta and the Roman Republic. He argued that such a balanced system could lend strength and prevent rapid changes in a state's political structure.