idiocy

n. [ From idiot; cf. Gr. &unr_; uncouthness, lack of education, fr. &unr_;. See Idiot, and cf. Idiotcy. ] The condition or quality of being an idiot; absence, or marked deficiency, of sense and intelligence. [ 1913 Webster ]

I will undertake to convict a man of idiocy, if he can not see the proof that three angles of a triangle are equal to two right angles. F. W. Robertson. [ 1913 Webster ]