Lack of knowledge. 

Nescience.— Ignorance regarding something about which one is not expected to have knowledge. Ignorance about something never known. 

Privative Ignorance.— Ignorance regarding something about which one previously had knowledge. 

Invincible Ignorance.— Ignorance that one, for whatever reason, cannot overcome. 

Vincible Ignorance.— Ignorance that one, for whatever reason, can overcome.