The text of the Fourth Amendment provides no guidance about what makes a search unreasonable or when warrants are required to make a search reasonable. The Supreme Court has had to craft a doctrine based on intuition, policy goals, and halfhearted stabs at history. This Article argues that the Court’s Fourth Amendment doctrine is stable when it roughly tracks the eighteenth-century common law protection of property, privacy, and liberty. When the Court has sought to provide more protection than the common law provided, the result has been an erratic doctrine that has gradually receded almost back to the common law contours. The most recent move away from a robust Fourth Amendment has been to reduce the application of the exclusionary rule. As there was no exclusionary rule at common law, and for over a century after the Fourth Amendment was ratified, further reductions in the rule’s application can be expected.