The phrase "declare true" essentially means to acknowledge or confirm the authenticity of something. Its antonyms are words that convey the opposite meaning to "declare true." Words like "deny," "dispute," "disprove," "refute," and "repudiate" negate the legitimacy or truthfulness of a statement. Other antonyms include "contradict," "oppose," "challenge" and "question." These words imply that the statement being declared true is not entirely accurate, and there is room for doubts or challenges. Therefore, it is important to consider both sides of an argument or statement, especially when attempting to declare anything as true.