Diagnosis means finding the cause of a disorder, not just giving it a name.

—Sydney Walker III

The practice of medicine often is considered to be both science and art because identifying the underlying causes of disease and establishing a diagnosis require that health care practitioners use a combination of scientific method, intuition, and interpersonal (communication and human relations) skills. Diagnosis relies on the powers of observation; listening and communication skills; analytical ability; knowledge of human anatomy (structure and parts of the human body) and physiology (the functions and life processes of body systems); and an understanding of the natural course of illness.

The editors of the fifteenth edition of Harrison's Principles of Internal Medicine (edited by Eugene Braunwald et al., McGraw-Hill, New York, 2001) explain that diagnosis requires a logical...