Knüpfer was a baker's apprentice for three years as a youth before moving to a large city where he worked in a cement factory and learned the trade of locksmithing. His friends persuaded him to marry, but the union was unhappy from the start. He was an alcoholic and an abusive husband, and mistrusted not only his wife but everyone he knew. He attempted suicide in 1902 and was committed soon afterwards.
It became evident that he had been having paranoiac delusions for years, and visions in which Christ explained why he was being persecuted. He told psychiatrists that "no one had suffered as much, not even Christ" (Prinzhorn 1972, p. 172).
His works can be divided into two categories, the formal religious images covered with oracular inscriptions and the paintings of memories from his youth. Both categories display a preoccupation with symmetry and a fascination with circles.
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