Two centuries ago Chief Justice John Marshall famously wrote that discretionary choices should not be left to a court’s “inclination, but to its judgment; and its judgment is to be guided by sound legal principles.” Unfortunately, for the next 177 years, federal criminal sentencing would be largely devoid of the substantive law and procedural rules necessary to guide judicial discretion. Congress passed the Sentencing Reform Act of 1984 (SRA) in response to increasing concern over unwarranted sentencing disparities in federal courts, thus creating the first real opportunity for the federal judiciary to develop a common law of sentencing. The SRA established the United States Sentencing Commission (“Commission”). The Commission is charged with developing and promulgating regulations governing federal sentencing that would emphasize fairness, consistency, punishment (retribution), incapacitation, and deterrence. To that end, the Commission designed the United States Sentencing Guidelines (“Guidelines”), which consisted of a set of mandatory narrow sentencing ranges for each defendant. The introduction to the Guidelines Manual outlines three congressionally mandated objectives of sentencing reform: honesty, uniformity, and proportionality.7 Honesty was intended to reduce sentencing disparity between time sentenced and time served, and to clarify the sources actually used to inform sentencing; uniformity was designed to reduce significantly interjudge disparity in sentencing for offenders with similar criminal histories and conduct; and proportionality was concerned with sentencing defendants in a manner consistent with the severity of their particular conduct.