This book provides the first comprehensive, historically based, philosophical interpretations of two texts of Thomas Percival’s professional ethics in medicine set in the context of his intellectual biography. Preceded by his privately published and circulated of 1794, Thomas Percival (1740-1804) published in 1803, the first book thus titled in the global histories of medicine and medical ethics. From his days as a student at the Warrington Academy and the medical schools of the universities of Edinburgh and Leyden, Percival steeped himself in the scientific method of Francis Bacon (1561-1626). McCullough shows how Percival became a Baconian moral scientist committed to Baconian deism and Dissent. Percival also drew on and significantly expanded the work of his predecessor in professional ethics in medicine, John Gregory (1724-1773). The result is that Percival should be credited with co-inventing professionalism in medicine with Gregory. To aid and encourage future scholarship, this book brings together the first time three essential Percival texts, , , and of 1823, the bridge from to the 1847 on the American Medical Association. To support comparative reading, this book provides concordances of to and of . Finally, this book includes the first Chronology of Percival’s life and works.