Abstract: Terror in the Balance: Security, Liberty, and the Courts (2007) advances a “trade-off thesis”: there exists a security–liberty frontier, such that policies below the frontier can be changed so as to improve both security and liberty, while if policy is already at some point on the frontier, neither security nor liberty can be increased without decreasing the other (the trade-off curve). Many commentators have launched critiques of the thesis, but none of them undermine it. Some redefine liberty as a component of security, or security as a component of liberty, while others make the point that not all policies are currently at the security–liberty frontier. These points are entirely consistent with the trade-off thesis; the critics err to the extent that they take these points as grounds for rejecting the thesis itself. No one has yet advanced an alternative framework that is both well-specified and analytically distinct from the trade-off thesis. Although the thesis is widely controverted, it should be common ground.