Antonyms, or words that have opposite meanings to "casts doubt on," can provide clarity and confidence to a statement or argument. Words such as "affirms," "confirms," "proves," "establishes," and "verifies" can help reinforce the veracity of a claim, rather than undermining it. By using these antonyms, one can assert the truth of a matter with certainty, without leaving room for skepticism or questioning. Additionally, words like "bolster," "support," "strengthen," and "corroborate" can provide evidence or justification for a position, further reinforcing its validity. Choosing the appropriate antonym can make a significant difference in the impact and efficacy of one's communication.