Decision making

Leo Tolstoy was even bolder: “The most difficult subjects can be explained to the most slow-witted man if he has not formed any idea of them already; but the simplest thing cannot be made clear to the most intelligent man if he is firmly persuaded that he knows already, without a shadow of doubt, what is laid before him.”

What's going on here? Why don't facts change our minds? And why would someone continue to believe a false or inaccurate idea anyway? How do such behaviors serve us?