Falsehoods are statements or positions which are inconsistent with known facts.  They come in a number of flavors.  Chief among these are misconceptions, delusions, and lies.  These distinctions are important, because each requires a different approach.

Misconceptions are often the easiest to deal with.  Someone who holds a misconception, when presented with the conflict between his statement and the facts, is likely to change his position to accommodate his new perception of the situation.  In argument, this is likely to lead to peaceful agreement, and progress.

Lies are more difficult.  A liar knows that his statement is false, but he makes it anyway.  He does this for personal gain, in the hopes that its falsehood will not be discovered.  When a liar is challenged, he may double down and deny the evidence, a course that often leads to prolonged bitterness and unsatisfactory outcomes for all involved.  He may admit the lie, which usually uncovers his motive as well.  This humiliates the liar and may lead to gloating by the victim of the lie; neither improves the situation.  If I lie goes undiscovered it becomes, functionally at least, a fact.  In argument, none of these is a desirable outcome.

Delusions are the most destructive of all.  Delusions are firmly held beliefs that are difficult or impossible to unseat.  They may be bizarre–fixed illusions that are impossible or wildly unlikely, like the belief that you are dead (Cotard delusion)—or non-bizarre—fixed illusions that might be true but are not, like the belief that a faithful spouse is cheating.  Delusional people may not experience any social or occupational impairment; especially when the delusion is non-bizarre, outward behavior may not seem unusual.  A person of high ability may achieve prominence and influence in business or society.  Only when discussion of the subject of the delusion arises does its persistent falsehood become apparent.  When a delusional idea is acted upon, bizarre behavior may result.

A number of different varieties of delusions are described.  The grandiose type shows inflated ideas of self-worth, knowledge, intelligence, royal identity, or a special relationship God.  The persecutory type includes a fixed idea that one is singled out for malevolent treatment by some great power or supernatural force.  The paranoid type typically shows some degree of grandiosity in its delusions.  The mixed type shows combined features of some of the other types.  Volatile episodes of sad or irritable mood may accompany all types.

Delusional disorder, as a mental illness, has been extensively studied.  People with delusions tend to filter incoming information, basing their decisions on the facts that best support their fixed beliefs and discarding the inconvenient truths.  They make decisions based on less information than control subjects need, yet are more certain of the correctness of their decisions.  They attribute negative events to external agencies, and have difficulty understanding the intentions and motivations of others.

Dealing with a delusion from the outside can be a challenge, especially when a person of exceptional intelligence or authority holds it.  Because the belief is deeply held, it is unlikely to be unseated by appeals to evidence or logic.  Direct challenge of a delusion produces a cognitive dissonance that may provoke unpredictable, and sometimes dangerous, behavior that aims at eliminating the conflict rather than the delusion—challenging your boss’s delusion is likely to get you fired.  Anger is a common response, and violence can occur.

It is best to avoid directly confronting a delusion, and to avoid engaging it, either.  Insight-oriented approaches (e.g. “fact checking”) rarely work.  Such approaches breed hostility and distrust in the holder of the delusion that make resolution of the issue more difficult.

Offering empathy, support, even flattery, can build rapport.  In such a supportive milieu, the maladaptive aspects surrounding the delusion can then be approached gently.  Socratic and hypothetical questions can be used to engage the idea of the delusion without directly challenging it, allowing the subject to continue to feel in control while contemplating the consequence of his beliefs.  Gradually, over months or years, a delusional system may be modified or eliminated in this manner, though it often does not work.  When a powerful deluded person surrounds himself with a circle of sycophants who engage his delusions, or there is an organized external effort to debunk his “falsehoods”, there is virtually no hope that the delusion will be dispelled.

The reason that the distinction among types of falsehood is important,  is that each type requires a different approach.  A person with a misconception is generally not at fault; he will admit the error, and correct his course when he sees the right path.  A liar is purposefully deceitful and should be called out for his lie.  If he admits it the conversation can continue, with due consideration given to the fact that at least one party is a liar; if he refuses to admit the lie despite adequate evidence, then he can be dealt with punitively, or at least excluded from the conversation.  The man with a delusion is not at fault, but is potentially dangerous.  He should be removed from the conversation without rancor, and offered help (which he will probably not accept.)

Correcting a misconception promotes understanding and progress.  Challenging a lie invites conflict but allows progress.  Treating a delusion as you would treat a lie invites havoc and impedes progress.  Challenging a delusion in someone with authority over you invites harm to both of you.