In the book’s opening, Sontag provides a clear pathway for the reader to the heart of the book’s intention, writing, “My subject is not physical illness itself but the uses of illness as a figure or metaphor” (3). Illuminating, elucidating, and liberating oneself form these metaphors of illness are essential for Sontag in finding “the healthiest way of being ill” (3).

Sontag begins with a frustration that is located in the metaphors that spring from two prominent diseases—tuberculosis (TB) and cancer. Both are difficult and deadly in an era of modern medicine where all sicknesses are assumed to be curable. TB claimed many lives as its cure remained elusive into the 20th century. Then, after TB was contained and a treatment was found, cancer took its place. What unites these two, other than their severity, is their mysterious character in the eyes of the public. It is this mystery that makes people treat the infected as objects of scorn or as pariahs. The ill-omened mystery of this disease becomes synonymous with its name, to the point where Karl Menninger, a prominent 20th-century psychiatrist, recommended avoiding using the names of diseases so as not to endanger the patient. Ultimately, all this avoidance and secrecy result in negative connotations attached to illness, such as disgrace, repugnance, and shame.