When we need to express an opposing view, there are several different phrases we might use instead of "assert the contrary." Common synonyms include "disagree," "contradict," "oppose," "object," and "challenge." Each of these terms carries a slightly different nuance, and the best choice will depend on the context and the speaker's tone. For example, "oppose" might suggest a more forceful or aggressive stance than "disagree," while "challenge" could imply that the speaker is questioning the veracity of the original statement. Ultimately, choosing the right synonym for "assert the contrary" can help to clarify and strengthen our argument, and ensure that our message is understood as we intended.