It seems there can be degrees of not knowing.
Not knowing that you do not know may be the lowest level of ignorance.
You think you know, but really you don’t know.
A lesser kind of ignorance may be knowing that you don’t know, but not caring to know more, or thinking the question cannot be answered–you have not wish to go further.
Then there is a not-knowing that knows it does not know and is curious if there is a way to know.
This not-knowing invites further inquiry and pulls us forward into learning.
It is not-knowing that is a vital part of knowledge.