The pioneering legal realist Jerome Frank once characterized Justice Oliver Wendell Holmes, Jr., as "The Completely Adult Jurist." By this he meant that Holmes had progressed beyond the "childish" search for absolutes in the law to the recognition that experience, rather than logic, was the proper lodestar for a judge to follow. There is another sense, though, in which Holmes demonstrated his maturity: As an associate Justice of the Supreme Court from 1902 through 1932, and as a retired Justice until his death in 1935, he served as mentor to a series of young Harvard Law School graduates who were paid by the United States Government to serve as his legal assistants, or to use today's term, his "law clerks." As a group, these men achieved extraordinary levels of professional success, particularly in the fields of legal academia and government service, and clerking for Holmes played a large part in that success. This fact was not lost on the clerks themselves. Alger Hiss, Holmes's clerk for the 1929-30 term, remarked that "'[i]t was probably the greatest emotional [and] intellectual experience any of us ever had .... I think Holmes was the single greatest influence on me."

While Hiss's career is hardly representative of his fellow clerks', his clerkship experience was similar to theirs in important ways, not the least of which was the veneration for Holmes that it instilled in him. He would have certainly agreed with Charles K. Poe, the very first of Holmes's protégés, who wrote to the Justice on the occasion of his ninetieth birthday and thanked him for "upset[ting] the notion that 'no man is a hero to his valet."' In reality, Poe and his successors were much more than "valets" for Holmes. They were his social and intellectual companions. It is this fact that makes Holmes a key figure in the transformation of law clerking from the primarily administrative institution it had been prior to the turn of the century into what can be termed a "noble nursery of humanity," wherein a young lawyer's intellectual curiosities could be awakened and valuable social and professional skills could be acquired. While Holmes did not invent the practice of hiring the top graduates of elite law schools to serve one-year terms as sounding boards in the chambers of federal judges (that distinction belongs to Horace Gray), his enormous popularity in the elite legal community enabled him to institutionalize the practice and to define the parameters of the law clerks' experience.