delusion

Firm and fixed belief in that which is based on inadequate grounding

A delusion is a fixed belief that is not amenable to change in light of conflicting evidence. As a pathology, it is distinct from a belief based on false or incomplete information, confabulation, dogma, illusion, or some other misleading effects of perception as individuals with these beliefs are able to change or readjust their beliefs upon viewing the evidence for these beliefs.

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