The antonyms for the word "open doubt" are "certainty," "belief," and "confidence." When someone has certainty or belief, they are completely convinced that something is true or accurate. They have no doubts or reservations about the matter. Confidence implies a similar level of certainty, but it also suggests a sense of self-assurance and conviction. When we have confidence in something, we not only believe it to be true, but we also feel confident in our ability to handle the situation or make the right decisions. These words represent a different mindset than "open doubt," and can be a source of strength and assurance.