In 1945 the French existentialist philosopher Maurice Merleau-Ponty (1907-1961) designated hallucinations as follows: "Since the hallucination is not a sensory content, there seems nothing for it but to regard it as a judgement, an interpretation or a belief... False perceptions are not perceptions at all. The victim of hallucinations cannot hear or see in the genuine sense of these words. He judges and believes that he sees or hears, but he does not really see or hear."
References
Merleau-Ponty, M. (1962). Phenomenology of perception. Translated by Smith, C. London: Routledge.
Dictionary of Hallucinations. J.D. Blom. 2010.