Fallacious
Fallacious adjective - Not using or following good reasoning.
Usage example: it's fallacious to say that something must exist because science hasn't proven its nonexistence
Valid is an antonym for fallacious.
Valid
Valid adjective - According to the rules of logic.
Usage example: your argument isn't valid because you're taking what should be the conclusion and using it as a premise
Fallacious is an antonym for valid.
Nearby Words: validity, validation
Both words in one sentence
- For extra rhetorical effect, this can be combined with Strawman Fallacy when your opponent has both fallacious and valid arguments, by refuting the fallacious arguments and ignoring the valid ones.
Source: Fallacy Fallacy - Seeing a wet sidewalk and concluding that there was rain is fallacious—not deductively valid—but it is not necessarily false, nor is it necessarily an unreasonable inference to make.
Source: Logical Fallacies
Cite this Source
Valid and Fallacious. (2016). Retrieved 2026, August 13, from https://thesaurus.plus/related/fallacious/valid
Fallacious & Valid. N.p., 2016. Web. 13 Aug. 2026. <https://thesaurus.plus/related/fallacious/valid>.
Valid or Fallacious. 2016. Accessed August 13, 2026. https://thesaurus.plus/related/fallacious/valid.
Google Ngram Viewer shows how "fallacious" and "valid" have occurred on timeline