The seriousness of the offender's crime -- not his need for treatment, his dangerousness, or the deterrence of others -- ought to be decisive in determining a sentence. Penalties must be scaled in accordance with the gravity of the offense, and departures from the deserved sentence should be impermissible, even if they may have some crime-control usefulness. The degree of likelihood that the offender might return to crime would be irrelevant to the choice of sentence, and indeterminate sentences would be abolished. Sentencing discretion would be sharply reduced so as to alleviate sentencing disparities. Imprisonment should be limited to serious offenses. The commensurate-deserts principle allows severe punishments only for serious crimes. Imprisonment is necessarily a severe penalty. Prison thus should be the sanction only for crimes, which cause or risk grievous harm, such as assault, armed robbery, and rape. Even for serious crimes, the length of imprisonment should be rationed, given the painfulness of the prison sanction. Penalties less severe than imprisonment would be for the nonserious offenses that constitute the bulk of the criminal justice system's caseload. Warnings, limited deprivations of leisure time, and perhaps fines would be used in lieu of imprisonment. Probation would be phased out because of its discretionary and treatment-oriented features.