This article examines a debate in the United States House of Representatives in 1789 and presents a case study of ad socordiam, which is shown to be an informal fallacy in the language of politics. This fallacy is based on inferences about covert intentions of speakers, depending in part on the level of the hearer’s epistemic vigilance. The study shows how an inference about a speaker’s intention can be substantiated on the basis of evidence even in the case of a historical debate. The present study advocates a view of pragmatics and discourse analysis that regards inferences about covert intentions as a legitimate object of investigation to provide a fuller picture of political debates involving deep disagreements and manipulation.