Definition.com
Hallucination is a word which has come to mean 'delusion', but its etymology means 'to wander in the mind'.
Definition.com
A Hallucination is a fact, not an error; what is erroneous is a judgment based upon it.
Definition.com
A Hallucination is a species of reality, as capable of teaching you as a videotape about Kilimanjaro or anything else that falls through your life.
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