Melissa Lane, Princeton's Class of 1943 Professor of Politics, traces how ancient thinkers theorized constitutional change and the search for stability. She starts with Polybius, a Greek hostage turned historian and tutor to Scipio, who asked how Rome conquered the known world and answered with a cyclical theory of constitutions sliding from kingship through aristocracy and democracy into mob rule before reverting to monarchy. Lane sets this against Plato's image of decline ending in tyranny and his more hopeful account of mixed constitutions, then brings in Herodotus's three simple constitutional types and Aristotle's six-fold scheme of good and corrupt rule. She works through three ways constitutions can be mixed, blending, co-presence, and counterbalancing, using Sparta's kings, elders, and assembly and Rome's consuls, senate, and popular assembly as test cases, including Polybius's rust metaphor for institutional decay. The lecture closes by tracing this mixed-government idea forward to Hobbes and John Adams. Recorded at Barnard's Inn Hall for Gresham College.