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

Class V. Words Releasing to the Voluntary Powers
Division (I) Individual Volition
Section III. Voluntary Action
2. Complex Voluntary Action

703. Artlessness.

   NOUN:ARTLESSNESS &c. adj.; inartificiality, unsophistication; nature, simplicity; innocence [See Innocence]; bonhomie [F.], naïveté [F.], abandon [F.], candor, sincerity; singleness of -purpose, – heart; honesty [See Probity]; plain speaking; épanchement [F.].
  rough diamond, matter-of-fact man; le palais de vérité [F.]; enfant terrible [F.].
   VERB:BE ARTLESS &c. adj.; be round with one [Shakespeare]; look one in the face; wear one’s heart upon one’s sleeve for daws to peck at; think aloud; speak -out, – one’s mind; be free with one, call a spade a spade; tell the truth, the whole truth, and nothing but the truth.
   ADJECTIVE:ARTLESS, natural, pure, native, confiding, simple, plain, inartificial, untutored, unsophisticated, ingénu [F.], unaffected, naïve; sincere, frank; open, – as day; candid, ingenuous, guileless; unsuspicious, honest [See Probity]; childlike; innocent [See Innocence]; Arcadian; undesigning, straightforward, unreserved, above-board; simple-minded, single-minded; frank-, open-, single-, simple- hearted.
  MATTER-OF-FACT, free-spoken, plainspoken, outspoken; blunt, downright, direct, unpoetical; unflattering, untrimmed, unvarnished.
   ADVERB:IN PLAIN -WORDS, – English; without mincing the matter; not to mince the matter (affirmation) [See Affirmation].
  1. Davus sum non Œdipus.—Terence
  2. Liberavi animam meam.
  3. As frank as rain on cherry-blossoms.—E. B. Browning