Perception can miss a reality because of darkness, blindness, distraction, hiddenness, or remoteness. 

• Darkness is obsurement due to absence of medium. Absence of light makes dark. A vacuum makes silent. 
• Blindness is a failure of reception. Failure of sight is blindness. Failure of hearing is deafness. 
• Distraction is a failure of attention. The eye is stimulated but vision doesn’t see. The ear is stimulated, but hearing doesn’t hear. 
• Hiddenness is a concealment of a reality by other realities. An object is hidden behind another object. A sound is masked by noise. 
• Remoteness is a vanishing in distance. A faraway object is too tiny to see. A faraway sound is too faint to hear.

Understanding can also miss a reality because of darkness, blindness, distraction, obscurity, or remoteness. 

• Darkness is an absence of medium — ignorance — lacking language or concepts needed to comprehend. 
• Blindness is a failure of reception — stupidity — mental weakness. 
• Distraction is a failure of attention — inattention — non-detection of patterns and connections. 
• Hiddenness is a concealment of realities by other realities — confusion –interference between unconnected concepts and confusion of categories.
• Remoteness is a concealment by distance — incuriosity — failure to see relevance.