In psychopathology, delusion is traditionally described as 1. a false firm conviction 2. whose truth is immediately evident to the person and requires no justification. 3. Their environment does not share the belief and in the cultural context, the opinion is considered false. In the development of psychopathology, this definition of delusion has been proposed, which is clear and clinically applicable. However, many researchers and neuroscientists argue that a logically unassailable definition of delusion is not helpful. The conventional definition probably only represents a delineation of part of the psychopathological phenomenon, which is not appropriate for the underlying problem.