Mawson, C.O.S., ed. (1870–1938). Roget’s International Thesaurus. 1922.

Class IV. Words Relating to the Intellectual Faculties
Division (I) Formation of Ideas
Section V. Results of Reasoning

487. Incredulity.

   NOUN:INCREDULITY. incredulousness; skepticism, free thought, Pyrrhonism; want of faith (irreligion) [See Irreligion]; minimifidianism; unbelief [See Unbelief. Doubt].
  SUSPICIOUSNESS &c. adj.; scrupulosity; suspicion (unbelief) [See Unbelief. Doubt]; inconvincibility.
  UNBELIEVER, skeptic or sceptic, miscreant [archaic], doubting Thomas, disbeliever, agnostic, infidel, misbeliever, nullifidian, minimifidian, zendik [Oriental], freethinker, Pyrrhonist (irreligion) [See Irreligion]; heretic (heterodox) [See Heterodoxy].
   VERB:BE INCREDULOUS &c. adj.; distrust (disbelieve) [See Unbelief. Doubt]; refuse to believe; shut one’s eyes to, shut one’s ears to; turn a deaf ear to; hold aloof; ignore, nullis jurare in verba magistri [L.].
   ADJECTIVE:INCREDULOUS, skeptical or sceptical, dissenting, unbelieving, inconvincible; hard of belief, shy of belief; suspicious, scrupulous, distrustful, disposed to doubt, indisposed to believe; heterodox.
  1. I’m from Missouri and I want to be shown.
  2. You call me misbeliever, cutthroat dog.—Merchant of Venice
  3. Knowledge of divine things, for the most part, as Heraclitus says, is lost to us by incredulity.—Plutarch