Binswanger and Siemerling's definition of hallucinations

   In 1907 the German psychiatrists Otto Bin-swanger (1852-1929) and Ernst Siemerling (1857-1931) defined hallucinations as follows. "We designate hallucinations as sense perceptions which, without stimulation of the sense organ involved by an external object, occur as a mere consequence of internal stimuli."

   References

   Binswanger, O., Siemerling, E. (1907). Lehrbuch der Psychiatrie. Zweite vermehrte Auflage. Jena: Verlag von Gustav Fischer.