A district court has broad discretion in deciding whether a suit may be maintained as a class action. Variations on this phrase populate the class action jurisprudence of the federal courts. The sentiment reflects the equity roots of the representative class proceeding—a history that has been thoroughly investigated by leading scholars in the field of civil procedure, structured the work of the committee that drafted modern Rule 23, and has repeatedly been embraced by the Supreme Court as a necessary starting point when interpreting and applying the Rule in modern practice. The power of the federal courts to exercise discretion when deciding whether to permit a suit to proceed as a class action has long been treated as an elemental component of a representative proceeding. It is therefore cause for surprise that there is no broad consensus regarding the nature and definition of this judicial discretion in the certification process. The federal courts have not coalesced around a clear or thorough exposition of the question, and the scholarly literature has not provided a sustained analytical treatment.