Ignorance is not having knowledge about something. For example, "Public ignorance about Covid 19 is a serious problem." It means that the public doesn't have correct information about the virus and that it's a problem. In your sentence, "cocksure" means to be too confident about something. It isn't a good quality. The writer tells us that being confident with incorrect facts or being confident with no knowledge of the facts is bad. Instead, we are told to be thoughtful and questioning about matters.

Ignorance is the state of not knowing or knowing little. To be ignorant is to know nothing or little. Example, He is ignorant. (he is dumb and knows little) He is ignorant of the situation. (he knows little about the situation you’re talking about) His ignorance is obvious. (His lack of knowledge is obvious) His ignorance of the situation is obvious. (He’s ignorant of the situation and it’s obvious) There is a well known expression, Ignorance is bliss This means that not knowing can be good (a joy) because sometimes knowing something is worse than not knowing.