Monomania

In medical jurisprudence. Insanity only upon a particular subject, and with a single delusion of the mind. The most simple form of this disorder is that in which the patient has imbibed some single notion, contrary to common sense, and to his own experience, and which seems, and no doubt really is, dependent on errors of sensation. It is supposed the mind in other respects retains its intellectual powers. In order to avoid any civil act done or criminal responsibility incurred, it must manifestly appear that the act in question was the effect of monomania.

Cyc. Prac. Med. "Soundness and Unsoundness of Mind;" Ray, Ins. § 203; 13 Ves. 89; 3 Brown, Ch. 444; 1 Add. Ecc. 283; 2 Add. Ecc. 402; Hagg. 18; 2 Add. 79, 94, 209; 5 Car. & P. 168; Burrows, Ins. 484, 485.

See "Delusion;" "Mania."