The antonyms of the word "art untruthful" are honesty, truthfulness, and sincerity. These words denote the opposite of something that is deceptive, misleading, or insincere. Honesty implies being free from deceit, cheating, or double-dealing, whereas truthfulness suggests being true to facts, straightforwardness, and accuracy. Similarly, sincerity connotes the quality of being genuine, earnest, and frank. In contrast, the word 'art untruthful' implies something that is fictitious, fabricated, or misleading, and does not represent the reality. In conclusion, using honest, truthful, and sincere art can create an authentic depiction of the world around us.