This is a study of Dr. William Cullen (1710-1790), the Scottish chemist, physician, and professor of medicine, who played a significant role in the Scottish Enlightenment. I argue that Cullen was both a more unorthodox figure in Scottish medicine than he is generally depicted, as well as a more ambitious one. Despite his controversial doctrines, he skillfully managed the hierarchy of his profession and reached the pinnacle of success as a learned physician in the Scottish Enlightenment. I explore Cullen’s life and thought from different angles. I explicate his pedagogical persona and philosophy of medicine, both of which shaped the experiences of his pupils. I show how his neurophysiology was rooted in his contentious interpretation of the nature of the nervous fluid. And I provide a detailed look at Cullen’s understanding of hygiene, or the art of health—a rarely-studied component of his practice of medicine.