Words have meaning. They are conveyances of logic and the very basis of rational thinking. Without an agreed upon understanding of the definition of words there can be no cohesive society, there can be no framework to hang a civilization upon. Words are designed to communicate. They are to send unambiguious meaning from one person to another. Every social contract is defined by words. Those words must have a precise meaning not subject to individual interpretation for the words to have any force, authority or meaning. Words work best when used to transmit truth, reality, logic. Words are harder to employ to transmit feelings or abstractions. Yes, they can transmit these "hard to nail down" things, but it requires more effort and artistry. Even so, these efforts rely even more heavily on words containing precise definitions.
Enter: the narcissist. The narcissist's use of language is a study in perversion. To pervert something is to misuse it. To debase it. To "misconstrue or distort". If language is the medium of clear communication, and it is, then to pervert the use of language is to use it to fend off communication. To obscure. To fend off understanding. To avoid committing to an idea. To throw you off the truth and send you down a blind alley so the con-artist can avoid exposure. To transmit false realities...i.e. lie. The narcissist hates nothing more than to have you hold him to his words. He reserves the right to change meanings of words, to make claims of never saying those words, to twist up your thinking with shifting definitions of words. He uses language to his own ends. He destroys social contracts by not allowing himself to be held to anything he says. He is a language anarchist. He is the antithesis of civilization. He is a danger to every society he finds himself in be it a family, a work place or a nation.
By his misuse of language he perverts his own mind. Over time we see the narcissist losing track of reality. We see him slipping further and further from the moorings of objective truth by his life time of perversion of truth into lies. His thoughts, which are designed to be organized by language, become disorganized and non-cohesive because words long ago lost their meaning to him. The shifting sands of redefining reality by redefining words have greased his palms and left him with no grip on truth. We see the aging narcissist become trapped in his delusions with no ability to find his way back to truth because now his mind can not work properly. His perversion of language eventually perverted his thinking. He is adrift ...cut off from true society by his misuse of his mind and his misuse of the great conveyance of thoughts by the vehicle of language.
Beware of those who misuse language. Pay attention to the words people use and hold them to what they say even if you are holding them to their words in your own mind without confronting them. If they won't "own" the words they choose to use when you proceed on their words as if they meant what they said, then consider that a red flag if a pattern of this behavior develops. Words have meaning. Words are the foundation of our thoughts and the most important medium for a cohesive society. The meaning of "is" isn't shifting and elusive. Know for yourself what words mean and don't allow someone to pervert what they mean in your own mind. This will allow you to live in reality. This will make it hard for anyone to brainwash you into believing a false reality. Words have meaning. Stick to the meaning and you'll get through life with your rationality intact.