This article examines the logic of necessity in eminent domain cases in the United States. While much has been written about "public use" justifications as adjudicated by courts, less attention has been paid to necessity. In part this is because public use is an explicit part of Fifth Amendment limitations on "takings" while necessity is part of the buried logic of sovereignty that grounds its exercise. Readings of pivotal cases from McCulloch to Kelo lead us to question recent attempts to revive necessity as a legal standard for reining in eminent domain power.