- Delusions are false beliefs that are deeply entrenched and clearly not based in reality. They are not consistent with cultural tenets or with the person's level of intelligence and life experience. Persons cling to these beliefs even after they are shown to be false.
When reading this definition, I can't help but be reminded of certain people. I'm sure you're experiencing a similar sort of Deja Vu as well. All of us know, or know of, people who cling to demonstrably false ideas, even in the face of conclusive proof that they are wrong.
There is no use trying to reason with such a person. They are blind, or at best indifferent, to the truth.
It isn't always easy, or even possible to determine what is true, but determining that something is false is usually not nearly as hard.