fallacy
false belief

In other words, these normal 4-year-olds have learned that others can be fooled by a false belief.

We can redact these false beliefs entire out of your mind and memory.

But it will stop the false belief that you've achieved something.

A delusion is a false belief held by a person.

They have a false belief that meats are essential to keep their children's good health.

A story from some years back dramatically illustrates the difference between true and false belief or faith.

And she is broken up in the false belief that I am untrue to her.

They may hold onto false beliefs, and cannot be swayed from them.

Thus had his actions been guided by a false belief.

Such a false belief would not be relevant in our present sense.