He declared ignorance on the subject

His ignorance on such matters is dangerous

Ignorance is the parent of fear, and being completely nonplussed and confounded about the stranger, I confess I was now as much afraid of him as if it was the devil himself who had thus broken into my room at the dead of night.

I questioned all my men, so as to be able to give a name to this corpse; but the crew's ignorance was as complete as mine: nobody knew the victim.

Ignorance is a reality on which we feed; science is a reality on which we fast

Ignorance breeds fear, and fear breeds hate

No happiness is possible in ignorance; certainty alone makes life calm

Ignorance of the facts led to a bad decision