This essay contains an approach to the moral thinking of Pellegrino. This first part addresses the elementary sources of Medicine identity, as seen by the author, which was the starting point for his research on the role of both physicians and Medicine, and led him to his proposal to reform medical ethics. His thinking is developed in four different scopes: 1) the ideal of medical education; 2) Medicine as a moral enterprise; 3) the medical humanities in the formation and professional life of physicians; 4) the philosophy of Medicine as source and origin of medical ethics.