Chapter 4 (Oath, Profession, and Autonomy) investigates the connections between medicine as incorporating an oath, being a profession, and possessing autonomy. It argues that professional medical practice cannot amount solely to a technique. Rather, it necessarily incorporates an internal medical ethic, to which practitioners swear. It argues that the most basic indisputable norm internal to medicine approximates the aphorism “as to diseases, practice two: help or do not harm”—primum, non nocere (or, “first, do no harm”). It details the implications of medical promising—including self-regulation, education of the public concerning the profession’s commitments, and societal respect for professional conscientious objection. Chapter 4 concludes by noting that the enduring legacy of the Oath—as seen in the renaissance of medical oath-taking in the White Coat Ceremony, for example,—consists in the conception and establishment of doctoring as a profession, a practice incorporating its own publicly avowed ethic.