Hervey M. Cleckley
Overview
Dr. Hervey Milton Cleckley (1903 - January 28, 1984) was an American psychiatrist
Psychiatrist
A psychiatrist is a physician who specializes in the diagnosis and treatment of mental disorders. All psychiatrists are trained in diagnostic evaluation and in psychotherapy...

 and pioneer in the field of psychopathy
Psychopathy
Psychopathy is a mental disorder characterized primarily by a lack of empathy and remorse, shallow emotions, egocentricity, and deceptiveness. Psychopaths are highly prone to antisocial behavior and abusive treatment of others, and are very disproportionately responsible for violent crime...

. His book, The Mask of Sanity
The Mask of Sanity
The Mask of Sanity is a book written by Hervey Cleckley, M.D., first published in 1941, describing the clinical interviews of Cleckley with incarcerated psychopaths. It is considered a seminal work and the most influential clinical description of psychopathy in the 20th century...

, originally published in 1941, provided the most influential clinical description of psychopathy in the 20th Century. The term "mask of sanity" derived from Cleckley's observations that, unlike people with major mental disorders, a "psychopath" can appear to be normal and even engaging, while typically not suffering overtly from hallucinations or delusions.
 
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