The Little Shaman is a spiritual coach & specialist in cluster B personality disorders, with a popular YouTube show and clients worldwide.
It's not uncommon for people who have to deal with narcissists to experience the narcissists changing, ignoring or outright denying facts on a regular basis. This is extremely frustrating, because for most of us, reality is based on facts. We live in a fact-based existence. There are things that happened, and things that did not happen. There are things that are demonstrably true, and things that are demonstrably false.
For example, if you go to the store with someone on Tuesday, it's probably not likely that on Friday one of you will suddenly decide that didn't happen. If you are having a good conversation with someone where both of you are laughing and enjoying yourselves, it's not likely one of you will suddenly decide tomorrow that this conversation didn't happen or that it was actually an argument. However, for people who have to deal with narcissists, this is exactly what happens every day. Reality is twisted, turned or even denied outright. A conversation becomes an argument. A joke becomes an insult. Events and happenings are "unhappened." They simply cease to exist. This is frustrating and crazy-making, because most people don't believe they can dictate reality. Most people don't believe they can just decide something did or didn't happen. It either happened or it didn't, and our thoughts or desires have no control over this fact.
This is not the way narcissists operate. Narcissists live in a world of make-believe, like a child. Anything that does not fit in with the narrative of that world is discarded as if it never happened. Retellings of the story will often omit the event and if they are confronted directly about it, they will often deny it happened at all. Other events are reframed to fit whatever narrative the narcissist is now advancing. This narrative can change over years or in a matter of minutes. Reality for a pathologically narcissistic person has nothing to do with anything that actually happened, and everything to do with what the narcissist feels happened. That's the kicker: narcissists believe feelings are facts. This is what dictates their reality, and it's one of the biggest reasons they are so difficult to deal with.
This is why they deny facts. Because to them, it is not a fact. To them, the fact is whatever their mood dictates it is. If they are angry at you, your comment was hurtful and they will explode with abuse and tantrum, or freeze you out with cold rage. If they are not angry with you, the exact same comment is the funniest joke they ever heard and they will laugh their head off. It has nothing to do with you or anything that is actually happening. It is all based on their feelings, which also have nothing to do with you or anything that is actually happening.
Pathologically narcissistic people are controlled by their inner landscape. They are self-centered and self-focused. They truly are wrapped up in their own little world, and it colors everything they see, do, think and feel. This inner landscape is inherently negative and abusive, and therefore their perception of the world is, too. It is almost impossible for them to perceive events as the events have actually happened, because their perception is so flawed. Because they are so self-centered, everything that happens and everything everyone does is perceived as being directed toward them, as having meaning for them. And because their feelings for themselves are so negative, this meaning is almost universally bad. Even if it isn't bad, per se, it will nearly always be distorted.
These perceptions can come across as paranoid or even delusional to other people, because most people don't understand someone being so incredibly self-centered. For example, the narcissist in your life may assign ludicrous meanings to songs you play in the car, believing them to be meant as a message for them. This can seem delusional or even psychotic if people don't understand the way the narcissist's mind works. It isn't a true delusion, and it isn't psychosis. It's that this person is so self-focused and so pathologically narcissistic that they do not understand there could be any motive for your actions that does not involve them. They don't understand that you are a person nor do they see you as one; you only exist in this world so far as how you relate to them, so they cannot understand that you might be playing the song just because you like it. Any explanation of this will be summarily disregarded. You have no likes. You have no choices. You have no personality. You have nothing. You are a reflection of their feelings and that's all. So you played the song because you like it? No, no, no indeed. That is not even considered. Their narcissism dictates that it has to be a message for them because they are the only reason anything happens. Ever.
The event - which in this example is a song being played - obviously triggered an emotional reaction in the narcissist that they found uncomfortable or overwhelming. If the song is sad, or about a relationship ending, for example, this would certainly trigger a fear or abandonment reaction, which would probably cause either anger or hysteria. And because they are so self-centered and narcissistic, they believe you acted purposely to create that reaction in them. Narcissists take responsibility for nothing, remember. Not even their own feelings. If they feel bad, it's because somebody made them feel bad. So the event is reframed as hurtful and malicious based on the narcissist's feelings and nothing else. All evidence to the contrary is ignored or denied.
This constant reframing and retelling of events to suit their mood is very frustrating for loved ones. What is OK one day is suddenly not OK the next. Even worse, what was good yesterday is bad today. One day, you are hanging out with the narcissist and having a great time. The next day, the narcissist becomes angry and when you ask why they are upset since you had such a good day previously, suddenly they insist you spent the entire previous day arguing. And you're confused. You're like, "So we weren't watching Golden Girls and laughing like hell over that joke Sophia made? You didn't say this or do that?" and they look you dead in the eye and say, "That never happened. You be nice to me? That'll be the day." And that really hurts people, because now the narcissist has not only ruined today, they've ruined what you thought was a good day, too. This kind of thing often creates a situation where loved ones can no longer bring themselves to be nice to the narcissist anymore. They have been burned and betrayed too many times. They've had the rug pulled out from under them so many times they start to figure, "What's the point? Even if I do try to be nice or get along, it doesn't even matter. They just unhappen everything good anyway."
This behavior can be simply lies and attempting to hurt someone, but it can also be because whatever does not fit with the narcissist's narrative or expectations is just discarded. Pathologically narcissistic people have two general narratives, diametrically opposed to each other but one just as delusional and unrealistic as the other. The first is the delusional positive-but-false regard they hold themselves in, and the other is the delusional negative-but-true regard that they hold themselves in.
Things that don't fit in with the positive-but-true regard would be things they've done wrong. This is the more fragle of the two belief systems, and it is easily shattered. It is more fragile because narcissists don't truly believe in it. Because it is more fragile, the mechanism here is basic denial. They know what really happened. They are simply putting things into a context that better-fits what they are comfortable with, or with what they need at that time. Events that run counter to this positive-but-false narrative will often be reframed to hold the narcissist blameless or they will be omitted from the retelling completely. For example, if the narcissist is out of control and you insist they leave the house, the event will be reframed as though you threw them out of the home for no reason. No mention will be made of anything they did. If you confront them directly, they will deny it. "I didn't do anything. You said you were tired of looking at me and threw me out. All I was doing was sitting here." This goes for anything else as well. Even if you show them tangible proof, they will still say it wasn't them. It's a very childish response. Kind of like if you catch a child with chocolate all over his face and candy bar wrappers all around him and you say, "Did you eat the candy?" and the child says, "What candy, Mommy?" So you say, "I see the chocolate all over your face and hands." and the child sees it too, but says, "I don't see any chocolate, Mommy." It's hilarious when it's a child, but when it's an adult, it's a little less funny.
If the things that don't fit into their positive-but-false regard for themselves are things they've done wrong, the things that don't fit in with the negative-but-true regard they have for themselves would be things you've done right. Narcissists believe they are worthless scum on the ground. They believe they are unlovable monsters with no redeeming qualities whatsoever. They don't really believe in the positive image they try to project onto the world, but they believe wholeheartedly in the negative one. It is not fragile or easy to break through. Because of that, the mechanism here is not usually denial. It's an actual problem with their reception of the information. Information that does not fit in with their belief that they are bad may be ignored completely or reinterpreted as negative to make it fit. It has to do with something in the brain called schema.
Without being too technical here, schemata are the way that your brain identifies and categorizes things. Like you have a staircase schema in your brain, so that when you see a staircase, you know what it is and what to do with it. If you didn't have that, every time you saw a staircase it would be a new experience. When something happens that your brain doesn't recognize, it searches for a category to put it in or it makes a new one. Let's say you love dogs and they love you, but then you get bitten by one. Most people's brains would not now lump all dogs into a "bad dog" schema. Their brain would create a new one for that particular dog. Narcissists seem to have more trouble than most people with this. They lump all people into one and expect bad behavior from all of them. Because their self-schemata are also negative, information that contradicts these is either distorted and twisted to fit or outright ignored and forgotten. Most narcissists also have trouble with something called object permanence. To make a long explanation shorter, problems with object permanence can create a situation where the information they have about a person gets "rewritten" with every interaction, kind of like a computer writing over an existing file. If the interaction is negative, all of the info their brain now has about this person is negative and all positive information has been lost. So when they say they can't remember that you were ever nice to them, they may be telling the truth.
This of course all happens behind the scenes, as it were. Narcissists are not aware of any of it. The only thing they are aware of are their feelings. And, as everything does with pathologically narcissistic people, it's come back around to feelings again. Feelings are the reason for everything with narcissists. I've spent however many minutes giving you the long answer, but the short one is that narcissists deny facts because whatever makes them feel good will be acknowledged and whatever makes them feel bad will be denied. That's pretty much it.
As an aside, people have asked if, since things like malfunctioning schema are beyond the narcissist's control, shouldn't they be held blameless for their behavior. The answer is no, they should not. They cannot control the way they think but they can control their behavior. If you don't believe that, inject a police officer into the situation and see how fast the narcissist gains control of themselves. Narcissists can control their behavior when they want to, and they know the difference between right and wrong. They know their behavior is wrong. They don't care. They believe their feelings justify it. They're wrong. "Justified" does not mean "right." It does not mean "excused." Just because you feel justified in hurting someone doesn't mean it's OK to do it.