Although it is widely accepted that the Eighth Amendment operates as a broad prohibition against excessive criminal sanctions, neither the courts nor the academic community have presented a unified account of what excessiveness means in the Eighth Amendment context. This absence of any larger theory of the Amendment has produced an increasingly disjointed body of case law, and left the legal community without a method of analyzing excessiveness claims as they arise. The purpose of this Note is to lay the initial groundwork for such a theory. This Note argues that the reason why no comprehensive theory of the Eighth Amendment has been developed is because courts and scholars have not framed their discussion in terms of the two theoretical questions raised by the Amendment’s sweeping prohibition of “excessive” criminal sanctions: (1) what substantive standard of decision should determine the outcomes of specific cases, and (2) what standard of review should courts apply when examining sentencing schemes enacted by the legislative branches? In examining these questions, this Note makes two important insights about the nature of the Eighth Amendment: first, that the substantive standard of decision governing the excessiveness prohibition is necessarily tied to an underlying theory of punishment that provides the normative baseline needed for the excessiveness inquiry; and second, that the appropriate standard of review for a criminal sanction adopted by the legislative branches ultimately must be derived from a theory of judicial review that defines the appropriate role of the courts in a democratic society. By structuring the inquiry in this way, this Note contends that it becomes possible to see the competing policy preferences that are implicated by the selection of one standard over another, and thereby forces us to undertake the difficult task of deciding which of these social values should inform interpretation of the Eighth Amendment.