What we really know
Have you ever run into someone who was totally convinced of something that you knew to be wrong? While this is common in political fields, it happens also in the business world. This is a type of ignorance that is not easily cured.
As human beings, it is normal to not know everything. It is normal to make assumptions all the time. We have to do that in order to cope with the world. Indeed, this ability to put a lot of things on "auto pilot" is what makes us able to do so well at hunting and raising children. But, when our deeply held assumptions are wrong, that is when we run into trouble.
This is such a common problem in software development that "ignorance" now has classifications.
Zero level ignorance is where I know something and can prove that I know it.
First level ignorance is when I know that I don't know something
Second level ignorance is when I don't know that I don't know something
Third level ignorance is when I don't know an efficient way to find out if I don't know something.
Just like trying to argue with someone about politics, curing ignorance when the person is not aware of being ignorant is an exercise in futility. In most cases, the person in question will resent you trying to "educate" them. Experience is often the only teacher that will be heard. It is an expensive education, but often that is the only way. As Mark Twain said, "A man who carries a cat by the tail will learn something he can learn in no other way."
However, such people can cause a lot of problems. Because of their certainty, they are able to mislead others. When looking at history, we see how the certainty that a specific way of life is the right one has caused environmental disasters, social upheavals, as well as political disasters. Many times, the cop who has just stopped someone has that action challenged with "Don't you know who I am?" Their certainty that they are correct prevents them from seeing how their actions are wrong.
In software development, the problem is often found in those who are sure that they know what is to be done. Many times, they jump in and start work on a project before all the details have come out. While it can be fun to do that, most cases that means that their work will be replaced later on in the project. Sometimes, their choices made too early can mean serious rework later on when a design has to be redone.
In business, often we have to tell people multiple times what needs to be done. The first times, people filter what we say through their own ideas of what needs to be done. It can be rather frustrating to go through the process over and over again before getting past the preconceived ideas.
Ignorance is a challenge. Yet, when we help people get past that ignorance, we get the best results.