JASPERS'S DEFINITION OF ILLUSIONS AND HALLUCINATIONS

In 1913 the German psychiatrist and philosopher Karl Jaspers (1883-1969) defined illusions and hallucinations as follows: "Illusionis the term for perceptions which in fact are transpositions (or distortions) of real perceptions; here external sensory stimuli unite with certain transposing (or distorting) elements so that in the end we cannot differentiate the one from the other.Hallucinationsare perceptions that spring into being in a primary way and are not transpositions or distortions, ofany genuine perception."

Jaspers, K. (1997).Generalpsychopathology. Volume 1. Translated by Hoenig, J., Hamilton, M.W. Baltimore, MA: Johns Hopkins University Press.