(n.) The condition or quality of being an idiot; absence, or marked deficiency, of sense and intelligence.

amentia arrested development asininity backwardness battiness blithering idiocy brainlessness buffoonery clownishness crackpottedness crankiness craziness cretinism daffiness desipience eccentricity fatuity fatuousness folly foolery foolheadedness foolishness frivolity frivolousness giddiness goofiness half-wittedness idiotism imbecility inanity ineptitude infantilism insanity lunacy madness mental defectiveness mental deficiency mental handicap mental retardation mindlessness mongolianism mongolism mongoloid idiocy moronism moronity niaiserie nugacity nuttiness profound idiocy queerness retardation retardment sappiness screwiness senselessness silliness simple-wittedness simplemindedness simpleness simplicity stupidity subnormality thoughtlessness triflingness triviality wackiness weirdness witlessness zaniness zanyism