Hallucination is the result of an extreme deprivation of outer sensation. In the same way that the lesser sensory data of cool media result in participation to fill in details, a lack of any sensory data results in extreme completion of the senses.[1] McLuhan refers to this concept much less than he does to the opposite, somnambulism; this may imply that he sees the effects of somnambulism everywhere, but hallucination is only a logical opposite that does not come about in media studies in general.
The opposite of hallucination is hypnosis.