Affected with a high degree of intellectual independence; not conforming to standards of thought, speech and action derived by the conformants from study of themselves; at odds with the majority; in short, unusual. It is noteworthy that persons are pronounced mad by officials destitute of evidence that themselves are sane. For illustration, this present (and illustrious) lexicographer is no firmer in the faith of his own sanity than is any inmate of any madhouse in the land; yet for aught he knows to the contrary, instead of the lofty occupation that seems to him to be engaging his powers he may really be beating his hands against the window bars of an asylum and declaring himself Noah Webster, to the innocent delight of many thoughtless spectators.
Ambrose Bierce’s definition of Mad in: An Eye for An I: Living Philosophy, ReadHowYouWant.com, 4 March 2008, p. 104.