Dogmatists' hallucinatory denials of reality
A replica of James Cook's ship Endeavour. According to legend, the original Endeavour was invisible to some aborigines in places that the ship visited.
The term "hallucination" is usually considered to mean the perception of things that do not exist. However, a "hallucination" can also be a failure to perceive something that does exist -- an encyclopedia broadly defines "hallucination" as a "false perception characterized by a distortion of real sensory stimuli." Examples of this second kind of hallucination are stories -- perhaps apocryphal -- that aborigines in places visited by European explorers were unable to see the Europeans' ships because the experience of the aborigines taught them that such large ships could not possibly exist. Dogmatists in different subjects -- e.g., Darwinism and the holocaust -- behave exactly like these aborigines, i.e., they simply cannot begin to comprehend anything that challenges their dogmatic beliefs. Arguing with them is like talking to a brick wall -- they will just ignore you, scoff at you, or present frivolous arguments.