Karl Leonhard (March 21, 1904 in Edelsfeld, Bavaria, Germany – April 23, 1988 in East Berlin, GDR) was a German psychiatrist, who stood in the tradition of Carl Wernicke and Karl Kleist. He created a complex classification of psychotic illnesses called nosological. His work covered Psychology, Psychotherapy, Biological psychiatry and Biological psychology. Moreover he created a classification of Nonverbal communication.

He was born as the sixth of eleven children, his father being a Protestant minister. His medical education (at Erlangen, Berlin and Munich) was completed in 1928 and he worked as a physician at psychiatric hospitals in Erlangen, then a year later Gabersee and from 1936 Frankfurt am Main, to which last he was called by Karl Kleist. During the period of the Third Reich in order to save his patients from being killed by means of the T-4 Euthanasia Program, he stopped making diagnoses that would endanger a patient. In particular he stopped making any diagnoses of schizophrenia.^{[citation needed]}

"The Man" is a slang phrase that may refer to the government or to some other authority in a position of power. In addition to this derogatory connotation, it may also serve as a term of respect and praise.

The phrase "the Man is keeping me down" is commonly used to describe oppression. The phrase "stick it to the Man" encourages resistance to authority, and essentially means "fight back" or "resist", either openly or via sabotage.

The earliest recorded use^{[citation needed]} of the term "the Man" in the American sense dates back to a letter written by a young Alexander Hamilton in September 1772, when he was 15. In a letter to his father James Hamilton, published in the Royal Dutch-American Gazette, he described the response of the Dutch governor of St. Croix to a hurricane that raked that island on August 31, 1772. "Our General has issued several very salutary and humane regulations and both in his publick and private measures, has shewn himself the Man." ^{[dubious – discuss]} In the Southern U.S. states, the phrase came to be applied to any man or any group in a position of authority, or to authority in the abstract. From about the 1950s the phrase was also an underworld code word for police, the warden of a prison or other law enforcement or penal authorities.