“The greatest enemy of knowledge is not ignorance; it is the illusion of knowledge.” – Stephen Hawking or David J. Boorstin
.
What is knowledge? It is the thoughts, ideas, understanding, facts or information acquired through learning and practice.
.
What is ignorance? Lack of knowledge, or information about something.
.
Knowledge improves if we keep on practicing more and more and adding information and facts into our brain. We should have some basic knowledge, a basic understanding to which we can relate to whatever we are going to learn, so that it makes the process of learning or gaining knowledge easier.
.
Ignorance (not having sufficient knowledge) is not a problem to learning, or of gaining knowledge….. But the illusion of already having knowledge is what prohibits us from gaining knowledge.
.
It is easier to understand if we think about it in a different way….. You try to practice ‘bunkai’ to a kata, or try to gain a deeper understanding of a principle, or technique you feel that you don’t know. By accepting that you don’t know, you then feel a keen interest towards knowing it, understanding it.
.
However, once you feel that you already know it, your brain, your thoughts, don’t pay much attention to it. You suffer from lack of concentration and conscious-focus on the matter that you are going to practice. Essentially ignoring it.
.
If you feel that you know enough about your martial arts, you may not show any interest to consume any further knowledge.
.
So the illusion (your ego) that you know it all, is what obstructs you from learning and gaining knowledge, gaining a deeper understanding.
.
The Dunning-Kruger effect is a type of cognitive bias in which people believe that they are smarter and more capable than they really are. Essentially, low ability people do not possess the skills needed to recognize their own incompetence. The combination of poor self-awareness and low cognitive ability leads them to overestimate their own capabilities. They just believe they are knowledgeable enough….. I am sure we all know someone like this.
.
Ignorance is something you can change. When someone doesn’t know, you can teach them…… When someone thinks they know, it’s way harder to make them accept something else, something new. 
.
“All I have learnt is that I know nothing. That too, it took me almost a lifetime to learn!”
.