Note 118:1 — Chapter V · Mad Folk in Comedy and Tragedy. (ii.) Imbecility.
Reading edition
Strictly speaking, the insanity of the imbecile is congenital; the general conformation of his brain is faulty, and the mental phenomena of his condition are for the most part “dissociated from active bodily disease.” (See Encyl. Brit., s.v. Insanity.)