“There is nothing,” wrote William Blackstone, “which so generally strikes the imagination and engages the affections of mankind, as the right of property.” Property continues to occupy a place of enormous importance in American legal thought. More than just a staple of the first-year law school curriculum, the concept of property guides the application of constitutional doctrines of due process and eminent domain. A grand division between “property rules” and “liability rules” classifies our common law entitlements. Property is a concept of such longstanding importance in our law, of such great inertial momentum, that it has expanded to include nonphysical property in goodwill, inventions, designs, artistic expression, symbols, secrets, privacy, and celebrity, as well as “new” property in social security benefits, government contracts, job security, and occupational licenses. Recent scholars have identified property with autonomy, personality, political participation, and reliance interests. Thus expanded, the concept of property threatens to disintegrate. If it includes everything, does it mean anything?