They live more or less close to the borderline of insanity as persons who have spells, eccentricities and peculiarities, hysteria, tics or just "nervousness."
"The Glands Regulating Personality"
Louis Berman, M.D.
Between prescience and imagination the borderline is ill defined.
"The Orchard of Tears"
Sax Rohmer
There was one question, however, that was indeed on the borderline, exceedingly difficult to answer in words, especially for scrupulous consciences; and that was whether they believed in the Pope's deposing power; and this question was adroitly and deliberately used by the Government in doubtful cases to ensure a conviction.
"By What Authority?"
Robert Hugh Benson