It's not ignorance does so much damage; it's knowin' so derned much that ain't so.

True wisdom is plenty of experience, observation, and reflection. False wisdom is plenty of ignorance, arrogance, and impudence.

Stupidity,--unconscious ignorance.

Ignorance ain't not knowin' stuff; ignorance is knowin' stuff that AIN'T TRUE.

Ignorance is the wet-nurse of prejudice.