Definitions from Black's Law Dictionary: 2nd Edition and Ballentine's Law Dictionary as are available for each term in each dictionary.
  • Ballentine's Law Dictionary

    A belief that something exists which does not exist and which no rational person in the absence of evidence would believe to exist. See 195 Pa. St. 291, 78 Am. St. Rep. 815, 45 Atl. 726.

  • Black's Law Dictionary: 2nd Edition

    In medical jurisprudence. An insane delusion is an unreasoning and incorrigible belief in the existence of facte which are either impossible absolutely, or, at least, impossible under the circumstances of the individual. It is never the result of reasoning and reflection; it is not generated by them, and it cannot be dispelled by them; and hence it is not to be confounded with an opinion, however fantastic the latter may be. Guiteau's Case (D. Ct) 10 Fed. 170. See Insanity.