The Eighth Amendment prohibition on “cruel and unusual punishment” places moral limits on what the state may do to people convicted of crimes. But because constitutional norms “are too vague to serve as rules of law,” courts need doctrinal standards to guide their analysis in concrete cases. In the American constitutional scheme, it falls to the Supreme Court to craft these standards.Translating constitutional values into workable rules will inevitably entail some cost to the full enforcement of those values, which makes the Court a site of ongoing struggle over the scope of constitutional protections. On paper, this struggle plays out in legal abstractions. Yet when the claimants are prisoners seeking to challenge the conditions of their confinement, the human stakes could not be higher. The greater the “slippage” between Eighth Amendment norms and their enforcement, the broader the judicial permission conferred on correctional officers to treat the incarcerated with cruelty — an effect that will cash out, every day, in increased physical suffering and psychological trauma for the real live flesh-and-blood people living in American prisons.